Plugged Pre-cat

Anything related to the factory RPO Crew Cab.

Moderator: F9K9

User avatar
HenryJ
Admin K Elite
Admin K Elite
Posts: 12705
Joined: Tue Oct 01, 2002 9:14 pm
Location: Ontario, Oregon
Contact:

Plugged Pre-cat

Post by HenryJ »

On the return trip and I guess, a little noticeable while pulling the hills on the way out for the extended memorial day weekend, the intake noise started to noticeably increase while the power decreased.

The temperature did rise a little quicker than usual, spark knock over 4000 rpm began to get worse.

Today it would barely make 50 mph, bogging the whole time.

After checking all the easy stuff (ignition, fuel, etc) I talked myself into the fact that it must be the cat.
Image

It was. The pre-cat was nearly completely plugged.

One of the ZR2 crowd has a 2001 Highrider that had a plugged pre-cat earlier this year, or last. He just replaced it with a straight pipe and has not set the SES light. So, that is what I will probably do.

What caused it? Modifications that I have done? Perhaps.
What caused the Highriders failure?

I'm not too worried, warranty would cover it since emissions are covered for at least 80K. But I'd rather be without it.

*Key words for search - precat pre cat
Last edited by HenryJ on Sat Jul 22, 2006 4:38 am, edited 1 time in total.

"Speed doesn't kill, suddenly becoming stationary does." - Richard Hammond
"Speed is just a matter of Money - How fast do YOU want to go?"-Mechanic from Mad Max-
If at first you don't succeed - Don't take up Skydiving!
- ThunderII KE7CSK
User avatar
a2b
Mod K Elite
Mod K Elite
Posts: 1765
Joined: Wed Oct 02, 2002 11:20 pm
Location: Los Angeles
Contact:

Post by a2b »

ya i had that problem when travelin thru tx. luckily, when the truck finally decided to go no further, it was right in front of a chevy dealership in the middle of nowhere :D
[size=75] -HOBIE

^^^^^^^^^^^^^^^^^| ||__\
| ##Budweiser ###### | ||''|"\,__.
|_...__...________ ====| |__|__|...]
"(@)'(@)""""**|(@)(@)******(@)I[/size]
User avatar
HenryJ
Admin K Elite
Admin K Elite
Posts: 12705
Joined: Tue Oct 01, 2002 9:14 pm
Location: Ontario, Oregon
Contact:

Post by HenryJ »

All fixed today, runs much better :thumb:

I had the muffler shop install BB chevy flanges , so the head pipe bolts to the pipe going to the cat.
This will allow me to "uncap" should the need arise. and should allow for easy removal of the cat should it also fail.

Pretty easily done . Cost $40 all parts and labor :D

Oh, FYI- 2 1/2" pipe from headpipe at the Y, to the cat. The cat is 3" in/out reduced to 2 1/2" in/out.

"Speed doesn't kill, suddenly becoming stationary does." - Richard Hammond
"Speed is just a matter of Money - How fast do YOU want to go?"-Mechanic from Mad Max-
If at first you don't succeed - Don't take up Skydiving!
- ThunderII KE7CSK
User avatar
quickbiker
Crew K Elite
Crew K Elite
Posts: 1575
Joined: Fri Oct 11, 2002 6:01 pm
Location: VA
Contact:

Post by quickbiker »

I had that happen to an 89 Commanche I had long ago. A long crow bar fixed it free of charge. :lol:
[size=75][url=http://outsideventure.com/s10crew/]01 S10 Crewcab - SAS'd[/url][/size]
User avatar
HenryJ
Admin K Elite
Admin K Elite
Posts: 12705
Joined: Tue Oct 01, 2002 9:14 pm
Location: Ontario, Oregon
Contact:

Post by HenryJ »

quickbiker wrote:I had that happen.... A long crow bar fixed it free of charge. :lol:
I actually planned on the same fix and hollowed it out, but wanted the additional clearance on the side for access to the servo and trans lines. Not to mention that the straight 2 1/2" pipe should flow better.

"Speed doesn't kill, suddenly becoming stationary does." - Richard Hammond
"Speed is just a matter of Money - How fast do YOU want to go?"-Mechanic from Mad Max-
If at first you don't succeed - Don't take up Skydiving!
- ThunderII KE7CSK
User avatar
2bunik
Crew Elite
Crew Elite
Posts: 434
Joined: Mon Jun 30, 2003 9:49 pm
Location: Mountain Home AFB , Idaho
Contact:

Post by 2bunik »

firstoff wow I like the emotions on the side.. ok but back to the plugged cat.. I agree with removing and replacing with a nice flowing straight pipe..
[size=75]TARMAC TRENDZ car club
2003 GMC Zr5 maroon or somethingto it.
Two 10s in a custom box and Pioneer Premier 400w amp, Quad mod,Body lift, bed light.
http://www.tarmactrendz.vze.com/[/size]
User avatar
HenryJ
Admin K Elite
Admin K Elite
Posts: 12705
Joined: Tue Oct 01, 2002 9:14 pm
Location: Ontario, Oregon
Contact:

Post by HenryJ »

Here's a picture of what I did...
Image

The BB chev. exhaust flanges allow for a quick disconnect should the cat have trouble in the future.

"Speed doesn't kill, suddenly becoming stationary does." - Richard Hammond
"Speed is just a matter of Money - How fast do YOU want to go?"-Mechanic from Mad Max-
If at first you don't succeed - Don't take up Skydiving!
- ThunderII KE7CSK
User avatar
Justin
Crew Elite
Crew Elite
Posts: 424
Joined: Mon Oct 28, 2002 8:15 pm
Location: RI
Contact:

Post by Justin »

any noticable power response? Deeper noise?
[size=75]05 Sierra LLY "Silver Bull"[/size]
User avatar
HenryJ
Admin K Elite
Admin K Elite
Posts: 12705
Joined: Tue Oct 01, 2002 9:14 pm
Location: Ontario, Oregon
Contact:

Post by HenryJ »

Justin wrote:any noticable power response? Deeper noise?
A huge difference over the plugged pre-cat ;)
It is really hard to compare, but it is probably about the same as it was with a good pre-cat, maybe slightly better?
The sound is a little louder, about the same for deep tonal qualities, and maybe just slightly "Tinnier" or "metallic" sounding. Not quite as mello as before, but there again the pre-cat had probably been plugging for quite some time.

"Speed doesn't kill, suddenly becoming stationary does." - Richard Hammond
"Speed is just a matter of Money - How fast do YOU want to go?"-Mechanic from Mad Max-
If at first you don't succeed - Don't take up Skydiving!
- ThunderII KE7CSK
User avatar
HenryJ
Admin K Elite
Admin K Elite
Posts: 12705
Joined: Tue Oct 01, 2002 9:14 pm
Location: Ontario, Oregon
Contact:

Post by HenryJ »

Here is a site that shows some of the damage and causes of converter failures-
Magnaflow website - converter failure
Magnaflow wrote:CATALYTIC CONVERTER FAILURES:
If a catalytic converter needs replacing, one of the problems below most likely
contributed to its failure.



Engine Tune-Up Required.
A number of problems could occur to the catalytic converter as the result of an engine that is out of tune. Any time an engine is operating outside proper specifications, unnecessary wear and damage may be caused to the catalytic converter as well as the engine itself. The damage is often the result of an incorrect air/fuel mixture, incorrect timing, or misfiring spark plugs. Any of these conditions could lead to catalytic converter failure or worse.



Excess Fuel Entering Exhaust.
The fuel that powers your vehicle is meant to burn in the combustion chamber only. Any fuel that leaves the combustion chamber unburned will enter the exhaust system and light-off when it reaches the catalytic converter. This can super-heat the converter far above normal operating conditions and cause a meltdown. Possible causes are an incorrect fuel mixture, incorrect timing, corroded spark plugs, a faulty oxygen sensor, sticking float, faulty fuel injector or a malfunctioning check valve.



Oil or Antifreeze Entering Exhaust.
Oil or antifreeze entering the exhaust system can block the air passages by creating a heavy carbon soot that coats the ceramic catalyst. These heavy carbon deposits create two problems. First, the carbon deposits prevent the catalytic converter from reducing harmful emission in the exhaust flow. And second, the carbon deposits clog the pores in the ceramic catalyst and block exhaust flow, increasing backpressure and causing heat and exhaust to back up into the engine compartment. Your engine may actually draw burnt exhaust gasses back into the combustion chamber and dilute the efficiency of the next burn cycle. The result is a loss of power and overheated engine components. Possible causes are worn piston rings, faulty valve seals, failed gaskets or warped engine components.



Deteriorated Spark Plug or Spark Plug Wires.
Spark plugs that don’t fire, or misfire, cause unburned fuel to enter the exhaust system. The unburned fuel ignites inside the converter and could result in a partial or complete meltdown of the ceramic catalyst. Spark plugs and spark plug wires should be checked regularly and replaced if damaged or if wires are worn or cracked.



Oxygen Sensor Not Functioning Properly.
An oxygen sensor failure can lead to incorrect readings of exhaust gasses. The faulty sensor can cause a too rich or too lean condition. Too rich and the catalyst can meltdown. Too lean and the converter is unable to convert the hydrocarbons into safe elements and may not pass a state inspection.



Road Damage or Broken Hangers.
The catalyst inside a catalytic converter is made from a lightweight, thin-walled ceramic. It is protected by a dense insulating mat. This mat holds the catalyst in place and provides moderate protection against damage. However, rock or road debris striking the converter, or improper or broken exhaust system support can cause a Catalyst Fracture. Once the ceramic catalyst is fractured, the broken pieces become loose and rattle around and break up into smaller pieces. Flow is interrupted and backpressure in the exhaust system increases. This leads to heat build-up and loss of power. Possible causes of a catalyst fracture are road debris striking the converter, loose or broken hangers, potholes or off-road driving.

A catalytic converter will rarely fail without a problem or malfunction occurring somewhere in the emission system in front of the converter. It is important to determine what caused the converter to fail so that the problem can be fixed and to prevent a recurrence of the failure.



Converter Meltdown.
This is an example of a converter meltdown. The converter was super-heated due to a raw fuel condition in the exhaust flow. The excess unburned fuel ignited when it struck the hot ceramic catalyst and drove the temperature far above the normal operating condition of the converter. The ceramic catalyst is unable to withstand the extremely high temperature and begins to melt. The ceramic collapses and the converter is destroyed. The melted ceramic may block the exhaust flow and cause additional damage to the engine. A converter glowing red-hot, or evidence of heat discoloration, confirms this situation.

The condition that led to this converter meltdown could be the result of a number of malfunctions including faulty oxygen sensor, an incorrect fuel mixture, worn spark plugs or plug wires, a faulty check valve, incorrect ignition timing, sticking float, faulty fuel injectors or other ignition malfunctions.



Carbon Deposits.
This is an example of a converter with carbon deposits in the ceramic catalyst. This is usually a result of oil or antifreeze entering the exhaust system or a too-rich fuel mixture. The heavy carbon deposit clogs the converter and reduces exhaust flow. This increases backpressure and causes the entire exhaust system to heat up. The heat backs up into the engine compartment and may result in a number of heat-related engine problems.

Mild carbon scoring may do less damage to engine components but it may seriously affect the converter’s ability to reduce harmful emissions. It could easily cause a vehicle to fail an emission test.

Carbon deposits may be the result of faulty valves, worn piston rings, worn or leaking gaskets or lead in the fuel.



Catalyst Fracture.
This is an example of a catalyst fracture. The ceramic became loose, cracked and began to break down. The pieces began to obstruct flow, creating backpressure and increasing the heat in the exhaust system. There is evidence of a partial meltdown in this example due to overheating.

The initial cause for this damage could have been road debris striking the converter based on evidence of impact on the converter shell. In some cases, if the protective mat that holds the catalyst in place is directly exposed to exhaust gasses, it could deteriorate and allow the catalyst to fracture. The Car Sound converter uses two recessed cavities in the body to hold the protective mat out of the exhaust flow to prevent any deterioration. The mat stays in place and the catalyst is held firm.
Last edited by HenryJ on Fri Jan 12, 2007 8:50 am, edited 3 times in total.

"Speed doesn't kill, suddenly becoming stationary does." - Richard Hammond
"Speed is just a matter of Money - How fast do YOU want to go?"-Mechanic from Mad Max-
If at first you don't succeed - Don't take up Skydiving!
- ThunderII KE7CSK
User avatar
killian96ss
Crew K Elite
Crew K Elite
Posts: 2669
Joined: Tue Sep 09, 2003 11:53 am
Location: Sacramento, California

Post by killian96ss »

What exactly is the purpose of the pre-cat? Is it for emission control, or sound deadening? Does removing it mean you won't pass smog? I want to get rid of mine to make a better flowing exhaust, but I want to make sure that it won't cause any problems with the smog refs here in CA.

Steve
User avatar
camelott112
Crew Elite
Crew Elite
Posts: 251
Joined: Tue Aug 17, 2004 1:59 am
Contact:

Post by camelott112 »

i know this is the s10 site but i have a 91 xploder that gurgles and sputters like a sone of a gun and i have tried just about everything i have come down to its either a riser making it misfire or i just need to get a 351 hehe you think it may be worth it to have them check that out i would love to get the jeep eater healthy again
User avatar
barch97
Crew K Elite
Crew K Elite
Posts: 1136
Joined: Thu Nov 21, 2002 11:08 am
Location: New Jersey
Contact:

Post by barch97 »

Kool-itcatalytic converter cleaner did wonders for my old dodge.

Image

Add it to a tank of gas or in severe cases... pour directly into carburator. :thumb:
User avatar
HenryJ
Admin K Elite
Admin K Elite
Posts: 12705
Joined: Tue Oct 01, 2002 9:14 pm
Location: Ontario, Oregon
Contact:

Post by HenryJ »

killian96ss wrote:What exactly is the purpose of the pre-cat? Is it for emission control, or sound deadening?
Emission control. It is smaller and warms-up faster. Kind of a head start on the catalytic conversion.
Does removing it mean you won't pass smog?
I'm not sure. There is one guy with a 2001 Highrider that removed his and did pass the smog test. I believe it was a sniffer test too.
Obviously the visual inspection would fail since you can not remove anything related to the emissions system. Some states are just using the OBDII inspection. If you don't throw a code, you pass. If that is the case you will be fine as mine has never thrown a code after removal.
I want to make sure that it won't cause any problems with the smog refs here in CA.
Find out what tests that they use for your year of vehicle. An anonymous phone call should answer some questions ;)

"Speed doesn't kill, suddenly becoming stationary does." - Richard Hammond
"Speed is just a matter of Money - How fast do YOU want to go?"-Mechanic from Mad Max-
If at first you don't succeed - Don't take up Skydiving!
- ThunderII KE7CSK
User avatar
killian96ss
Crew K Elite
Crew K Elite
Posts: 2669
Joined: Tue Sep 09, 2003 11:53 am
Location: Sacramento, California

Post by killian96ss »

HenryJ wrote:
killian96ss wrote:What exactly is the purpose of the pre-cat? Is it for emission control, or sound deadening?
Emission control. It is smaller and warms-up faster. Kind of a head start on the catalytic conversion.
Does the pre-cat help extend the life of the cat? What is all that crap that fell out of your pre-cat? It would seem that the air injection system would be sufficient enough to warm up the cat at start up by leaning it out. I have found that even the air injection system is almost pointless as well. For example, I was able to remove the same exact system on my Impala without any smog problems since I purchased a sticker from GM that says the air pump on this vehicle has been disabled and is no longer needed for emission control. The only down side to this would be a somewhat shorter life span for the cat. The upside is a much cleaner engine compartment and 22lbs of junk that has been removed. Yes, I actually weighed all the crap since I am trying to make this car faster. I like your setup with the flange, as it should help disassembly in the future. So I would need a 2-1/2" pipe after the Y and it would have to flare to 3" at the cat? Does this sound right?

Steve
User avatar
HenryJ
Admin K Elite
Admin K Elite
Posts: 12705
Joined: Tue Oct 01, 2002 9:14 pm
Location: Ontario, Oregon
Contact:

Post by HenryJ »

killian96ss wrote:...Does the pre-cat help extend the life of the cat?
It might, but if things are running correctly and there is no physical damage to the cat , it should outlive the engine , I would think. Therefore it may be overkill? Or at least an attempt to further reduce emissions?
What is all that crap that fell out of your pre-cat?
The melted down/ plugged honeycomb core
... So I would need a 2-1/2" pipe after the Y and it would have to flare to 3" at the cat? Does this sound right?
2 1/2" on both ends. It only needs to be flared enough to fit over the 2 1/2" pipe. The cat is 3" in/out , but you would have to cut right up close to get it to that inside diameter.

"Speed doesn't kill, suddenly becoming stationary does." - Richard Hammond
"Speed is just a matter of Money - How fast do YOU want to go?"-Mechanic from Mad Max-
If at first you don't succeed - Don't take up Skydiving!
- ThunderII KE7CSK
User avatar
F9K9
Mod K Elite
Mod K Elite
Posts: 6183
Joined: Sun May 30, 2004 12:26 pm
Location: London, Kentucky, United States

Post by F9K9 »

Mine wasn't plugged but, I was having overheating and mileage issues.
f9k9 wrote:Welll, just had the precat removed. The tech said that it had a couple of bad places but, advised it wasn't bad :( I'll try to post pics if, anyone thinks they can tell one way or the other. It has got to be a serious restriction of exhaust flow . The point of light in the pics are of the other end. They are the same size on both ends.

Image
Image
Image
Removing my pre-cat had a couple nice benefits :)
f9k9 wrote:Another Update
Looks like the the over heating issue is finally solved. The removal of the pre-cat was the final piece of the puzzle. I just completed a minor highway trip with temps at 95°. My gauge never went over 205° and I was in stop and go traffic for awhile. An added bonus was that I got 15.4 mpg which may not seem like much to you but, it's about 5 mpg better that I got going to Hot Springs last year. That's with rolling 33/10.50 meats and the roof rack. I would venture to guess the rack eats 2 mpg easily.
[size=75][b]"For those who have fought for it, [i][color=red]FR[/color][color=white]EE[/color][color=blue]DOM[/color][/i] has a taste that the protected will never know."
[url=http://www.naxja.org/forum/showthread.php?t=73349]GUIDE TO SEARCHING. [i] (Some of the forum software is different but, it has helped me a lot.)[/i][/url][/b]
[b]"Those who don't know history are destined to repeat it." Edmund Burke[/b][/size]
User avatar
HenryJ
Admin K Elite
Admin K Elite
Posts: 12705
Joined: Tue Oct 01, 2002 9:14 pm
Location: Ontario, Oregon
Contact:

Post by HenryJ »

Catalytic Converter - By Larry Carley
Catalytic converters are one of the greatest emission add-ons ever to be installed on vehicles. By cleaning up the pollutants left over from combustion, they reduce tailpipe emissions of hydrocarbons (HC) and carbon monoxide (CO) to extremely low levels, when everything is operating normally, that is. But sometimes things do not operate normally, and when that happens engine performance may suffer or the vehicle may fail an emissions test.
catalytic converter

Driveability symptoms such as a drop in fuel economy, lack of high speed power, rough idle or stalling are classic symptoms of excessive backpressure due to a plugged converter. Checking exhaust backpressure and/or intake vacuum will tell you if there's a blockage (more on this subject in a minute).

Elevated HC and CO tailpipe emissions, on the other hand, are often symptoms of a fouled converter or a faulty air supply (bad or leaky air pump, diverter valve or pulse air system). A fouled converter may not cause any increase in backpressure, so other methods of checking the converter are required for this type of problem (which we'll also get to shortly).

The important point to remember here is that converters don't just plug up or die for no good reason. There is usually an underlying cause which must also be diagnosed and corrected before the problem can be eliminated. Diagnosing a plugged or fouled catalytic converter is only half the fix. Replacing a bad catalytic converter will only temporarily restore things to normal because unless the underlying problem that caused the original converter to fail is identified and fixed, the replacement converter will likely suffer the same fate.

CONVERTER OPERATION
Under normal operating conditions, the converter should not have to work very hard to accomplish its job. If an engine has good compression, is not sucking oil down the valve guides, and the fuel, ignition and engine management system are all working properly, there should be relatively little HC and CO in the exhaust for the converter to burn (a few tenths of a percent CO and less than 150 ppm of HC when the engine is warm). In many late-model engines with multipoint fuel injection, combustion is so clean that the converter has little to do and the difference between the inlet and outlet temperature may only be 30 degrees F at 2,500 rpm � which is a lot less than the old rule of thumb that says a good converter should show at least a 100 degree F difference fore and aft at cruise. At idle, the converter in many late-model vehicles may cool off so much that there's almost no measurable difference in fore and aft temperatures. So checking exhaust temperatures fore and aft of the converter at idle and 2,500 rpm may not be the most accurate way to determine if the converter is working or not.

One thing temperature measurements will tell you, however, is if the converter is working too hard. An infrared noncontact pyrometer or a temperature probe will tell you if the converter is running unusually or dangerously hot. If the converter outlet temperature is 200 or more degrees higher then the inlet temperature, it means the engine is running rich and there's a lot of CO in the exhaust that needs to be burned. A rich fuel mixture will often produce a "rotten egg" odor in the exhaust (the smell is hydrogen sulfide). Underlying problems may include an engine management system that is not going into closed loop (check the coolant and oxygen sensors, or for a thermostat stick in the open position), plugged PCV valve, or excessive fuel pressure (bad fuel regulator). High CO levels in the exhaust can also be caused by an inoperative air pump system.

If the outlet temperature is a lot hotter (more than 500 degrees F) than the inlet temperature, it indicates unburned fuel in the exhaust. The most likely cause would be ignition misfire (fouled spark plug, shorted or open plug wire, cracked distributor cap, arcing rotor or weak coil), or a compression leak (burned exhaust valve). But other causes may include lean misfire (check for vacuum leaks, leaky EGR valve, low fuel pressure or dirty injectors). A single misfiring spark plug can cause an increase in HC emissions of 2,500 or more parts per million, which can push the converter's operating temperature well above its normal range.

A common external clue of overheating to look for is a badly discolored or warped converter shell.

CAUSES OF CATALYTIC CONVERTER PLUGGING
Prolonged overheating or short term severe overheating are the leading causes of catalytic converter plugging. The underlying cause here is often fouled or misfiring spark plugs, or a burned exhaust valve that leaks compression and allows unburned fuel to pass through the combustion chamber into the exhaust.

The average light off temperature at which the catalytic converter begins to function ranges from 400 to 600 degrees F. The normal operating temperature can range up to 1,200 to 1,600 degrees F. But as the amount of pollutants in the exhaust go up, so does the converter's operating temperature. If the temperature gets up around 2,000 degrees F or higher, several things happen. The aluminum oxide honeycomb begins to degrade and weaken. The platinum and palladium coating on the honeycomb also starts to melt and sink into the ceramic substrate reducing its effect on the exhaust. This accelerates the aging process and causes the converter to lose efficiency.

If the overheating condition persists for a long period of time, or if the temperature soars high enough, the honeycomb itself may breakdown and melt forming a partial or complete obstruction and causing a sharp rise in backpressure. A complete blockage will cause the engine to stall shortly after starting, and will not allow exhaust to exit the engine.

Some degree of restriction inside the converter honeycomb can also be caused by accumulated deposits: phosphorus from oil burning and/or carbon from oil burning, a rich fuel mixture or frequent short trip driving where the converter rarely reaches light-off temperature). Physical damage to the honeycomb as a result of road hazards or severe jolts may cause the relatively brittle ceramic honeycomb to break or crumble inside the converter shell. A rattling noise when you shake or thump the converter would tell you there's loose debris inside. A undamaged monolith converter should make no noise.

EXHAUST BACKPRESSURE CHECKS
To diagnose a plugged catalytic converter, you can check intake vacuum or exhaust backpressure. To check intake vacuum, connect a vacuum gauge to a vacuum port on the intake manifold. Start the engine and note the vacuum reading at idle. Then increase engine speed to about 2,500 rpm and hold steady. Normal vacuum at idle for most engines should be 18 to 22 inches Hg. When the engine speed is increased there should be a momentary drop in vacuum before it returns to within a couple of inches of the idle reading. If the vacuum reading is lower than normal and/or continues to drop as the engine runs, it probably indicates a buildup of backpressure in the exhaust. Remember, though, that intake vacuum can also be affected by retarded ignition timing and valve timing. What's more, some engines are much more sensitive to small changes in intake vacuum than others, so checking backpressure rather than intake vacuum may give you a better indication of what's going on.

Checking backpressure requires connecting a pressure gauge to the exhaust system. Use a gauge that reads up to 8 to 10 psi and is calibrated in 1/2 inch increments. Or, use a metric pressure gauge calibrated in kilo-Pascals (kPa). One psi equals 6.895 kPa.

A backpressure gauge can be connected to the exhaust system one of several ways: by removing the oxygen sensor and connecting the gauge to the hole in the exhaust manifold; by removing the air check valve in the air pump or pulse air system and connecting the gauge here; or by drilling a small hole into the head pipe just ahead of the converter to attach the gauge (never drill a hole into the converter itself!). One drawback of drilling a hole is that the hole will have to be plugged by a self-tapping screw, plug or welded shut after you've taken your measurements. Also, drilling is not recommended if the head pipe has a double-wall construction.

Once you've made your connection, start the engine and note the backpressure reading. Depending on the application, the amount of backpressure that's considered "normal" will vary. On some vehicles, backpressure should read near zero at idle, and should not exceed 1.25 psi at 2,500 rpm. Others can handle 0.5 to 1.25 psi at idle, but should have more than 4 psi during a snap acceleration test.

If you find a relatively high backpressure reading (say 8 to 10 or more psi), there's obviously an exhaust restriction that will require further diagnosis. Don't jump to conclusions and assume the converter is plugged because it might be a collapsed pipe or muffler.

One way to rule out the pipes and muffler is to visually inspect the exhaust system for damaged components. Another way is to drill a small hole in the pipe aft of the converter and check backpressure here. If the reading is lower (or is less than about 1 psi), the rest of the system is OK and the converter is what's causing the restriction. Or, disconnect the exhaust pipe aft of the converter. No change in backpressure would indicate a blockage at or ahead of the converter. If backpressure drops back to normal, the problem is not the converter but a collapsed pipe or muffler.

If you suspect the converter is plugged, you can disconnect and remove it. Then hold a shop light by one end of the converter and look in the other end. If you can't see the light shining through the honeycomb, the converter is plugged and needs to be replaced.

You can also recheck backpressure readings with the converter removed. If readings are at or near zero, you've found the problem. But if backpressure is still high, there's an obstruction in the head pipe or manifold. Sometimes a collapsed inner tube inside a double-wall head pipe will create an obstruction that acts just like a plugged converter. Another cause can be a heat riser valve on an older V6 or V8 exhaust manifold stuck in the closed position.

CAUSES OF CATALYST FOULING
To clean the exhaust, the catalyst inside the converter must be exposed to the hot exhaust gases. Lead, phosphorous and silicone can contaminate the catalyst and prevent it from working its magic. Lead used to be the most common contaminant, but is no more since it was eliminated from gasoline. Phosphorus is still a threat, and comes from motor oil. So if an engine is burning oil because of worn valve guides or rings, phosphorus will shorten the life of the converter. Blue smoke in the exhaust and an emissions failure are pretty good clues that the converter has been fouled with phosphorus.

The new "SJ" rated motor oils contain less phosphorus than earlier SH rated oils. The difference isn't much (about 20% less compared to SH oils), but over time the lower level of phosphorus reduces contamination to extend the life of the converter.

Silicone can find its way into the exhaust if the engine develops an internal coolant leak through a crack in a combustion chamber or a head gasket. Silicone will ruin the oxygen sensor as well as the catalytic converter, so chances are if the converter has been fouled the O2 sensor will also need to be replaced. White smoke in the exhaust is a clue that there's an internal coolant leak.

CATALYTIC CONVERTER OPERATING EFFICIENCY
If a converter is not plugged and passes exhaust normally, and there are no other engine performance problems (fuel, ignition and compression all OK, and the computer going into closed loop), but HC and CO levels in the exhaust are higher than they should be, the converter may be fouled. Most original equipment converters are designed for a service life of well beyond 100,000 miles, so if the converter has failed at low mileage contamination may be the culprit.

Checking converter operating efficiency can be done several ways. One "low tech" method is to make the fuel mixture momentarily rich by disconnecting the MAP sensor, or by creating excess HC in the exhaust by disconnecting and grounding a plug wire. Either condition should make the converter's operating temperature rise sharply, with the outlet temperature rising several hundred degrees over the inlet temperature. No change in temperature would tell you the catalyst is fouled and nothing is happening. Do not run this test for more than about two minutes because there's a risk of overheating and damaging what might be a good converter. Also, disconnecting the MAP sensor will likely set a trouble code, and on OBDII-equipped vehicles pulling a plug wire may set a misfire code.

The better approach is to read the composition of the exhaust gases with a 4- or 5-gas exhaust analyzer. A number of companies sell small portable exhaust analyzers that are relatively affordable ($2,500 to $5,500) and can be used for a variety of diagnostic purposes.

Checking emission readings at the tailpipe will tell you whether or not they are within normal ranges and help you diagnose the cause if emissions are high. Doing a "cold start" emissions check when the engine is first started will tell you if there are any engine problems that need attention. A cold start, in this situation, is when the converter has cooled down for at least 20 minutes. It will take a couple of minutes for the converter to warm up to light off temperature, so during this time you have a relatively clear window of what's coming out of the engine. When the converter reaches operating temperature, there should be a measurable drop in HC and CO readings (the amount will depend on how dirty the baseline readings were). No change in readings would indicate a dead converter.

Another test is to create a momentary rich condition or a misfire (as described earlier) to see if the converter can clean it up. As the converter starts to react to the excess pollutants, it's operating temperature should go up as the tailpipe emission readings come down.
OBD II CATALYST MONITOR

On 1996 and newer vehicles with OBD II onboard diagnostics, the OBD II system has a catalyst monitor to keep an eye on converter operating efficiency. The OBD II system compares O2 sensor readings upstream and downstream of the converter. If the downstream readings start to match those of the upstream O2 sensor, it indicates a drop off in operating efficiency and sets a catalyst code P0420. Other converter faults may set codes ranging from P0420 to P0439.
REPLACE CONVERTER

If the converter is plugged, contaminated, damaged or rusted out, it must be replaced. Likewise, if the OBD II system is showing low catalyst efficiency, the converter must be replaced. Replacing the catalytic converter will restore proper emissions performance. But a new converter will suffer the same fate as the old one if the underlying condition that caused the converter to fail has not been diagnosed and repaired. Look for fouled spark plugs or wires, low or no cylinder compression in one or more cylinders, or a computerized feedback system that stays in open loop all the time (bad coolant sensor, bad oxygen sensors, etc.).

On a dual-cat system, the side with the bad converter code will tell you which cylinder bank to check. If the converter on the right is bad, for example, check the O2 sensor, spark plugs and compression on the right cylinder bank.

Always replace the oxygen sensor. Converters needs an air/fuel mixture that is constantly flip-flopping from rich to lean. If the oxygen sensor is sluggish or dead, the fuel feedback loop will flip-flop too slowly or remain rich all the time.

Also check the air pump (if equipped) and related plumbing as these components provide fresh air for the converter to reburn the pollutants in the exhaust. If the air pump is not working right, it can reduce the operating efficiency of the catalytic converter significantly.

"Speed doesn't kill, suddenly becoming stationary does." - Richard Hammond
"Speed is just a matter of Money - How fast do YOU want to go?"-Mechanic from Mad Max-
If at first you don't succeed - Don't take up Skydiving!
- ThunderII KE7CSK
Shooter
Regular
Regular
Posts: 11
Joined: Wed Oct 08, 2008 7:52 am
Location: Michigan

Post by Shooter »

Newbie here, with a question on this old thread; sorry bout bringing up old threads.

I had just put on a magnaflow high flow cat last year bout this time. While I was at the dealership getting my second fuel pump put in ( under warrantee) I had my bud check the ses light that was on. He told me it was P0420 B1. He went on to tell me that I need a new cat. Then one of the other mechanics told me that it is prolly the pre cat that triggered the ses light because of the B1 (bank 1) Does this make any sense ? I figured I would just get rid of the pre cat anyway but I hate to have the ses light come on all the time.

By the way I have a 2003 crew, with a few mods inside and out. I used to be a member of mys10.com but now the site has closed.
User avatar
WileyHunter
Crew Elite
Crew Elite
Posts: 134
Joined: Sun Dec 09, 2007 7:57 pm
Location: Batesville, IN

Post by WileyHunter »

First, Welcome Aboard!!!

I don't think anyone will whip you for bringing out the old thread. It's better than starting a new one for a rehashed topic without searching.

While I don't know for certain, what you said about bank 1 makes sense to me. I know there are several members that are running with a pre-cat'ectomy' and planned on doing it myself one of these days on my '03.

Someone here with more 'mod' experience than myself will answer you fully I'm sure. It may take a little while though as a few of the heavy modders are on a trip together and my not be able to access the site daily.

Good luck.
WH
Shooter
Regular
Regular
Posts: 11
Joined: Wed Oct 08, 2008 7:52 am
Location: Michigan

Post by Shooter »

Thanks WH.

I think I'm just going to get the job done. My hope is that the ses light will stay off, after the work. My first thought was that the bank 1 was the first O2 sensor, which I have not replaced as of yet, so if I dont have to change that I'll be happy.

Thought I'd try and post some pics of my beast on here when I get some time. I also have a 1940 streetrod project if anyone is interested in seeing the progress on that.
Shooter
Regular
Regular
Posts: 11
Joined: Wed Oct 08, 2008 7:52 am
Location: Michigan

Post by Shooter »

I got my pre cat operation done today; hopefully the ses light stays off. It sounds a little better than it did before the operation. My ses codes were 420, 455, 442. The last two are the evap system, what a drag man
User avatar
Rockrz
Crew Elite
Crew Elite
Posts: 414
Joined: Sat Nov 17, 2007 7:18 am
Location: Texas

Post by Rockrz »

HenryJ wrote:I had the muffler shop install BB chevy flanges...
Wow, you must be on really good terms with that muffler shop considering they cfould get in trouble for removing an exhaust emissions device and replacing it with a straight pipe.

I need to find a shop like that :D
User avatar
Horsehammerr
Crew Elite
Crew Elite
Posts: 779
Joined: Sun Apr 15, 2007 2:03 pm
Location: Kimberling City, MO.

Post by Horsehammerr »

My shop would not do the removal part but, if I brought it to them with the pre-cat missing they could weld in a length of pipe as an " exhaust leak repair " !! No foul on their part. So out came the Sawsall and instant precat chop chop. Wow the thing must have fell out. :D 8)
User avatar
HenryJ
Admin K Elite
Admin K Elite
Posts: 12705
Joined: Tue Oct 01, 2002 9:14 pm
Location: Ontario, Oregon
Contact:

Post by HenryJ »

Rockrz wrote:
HenryJ wrote:I had the muffler shop install BB chevy flanges...
Wow, you must be on really good terms with that muffler shop considering they cfould get in trouble for removing an exhaust emissions device and replacing it with a straight pipe.
They did not remove it.

"Speed doesn't kill, suddenly becoming stationary does." - Richard Hammond
"Speed is just a matter of Money - How fast do YOU want to go?"-Mechanic from Mad Max-
If at first you don't succeed - Don't take up Skydiving!
- ThunderII KE7CSK
Shooter
Regular
Regular
Posts: 11
Joined: Wed Oct 08, 2008 7:52 am
Location: Michigan

Post by Shooter »

The guy told me that "seeing as there are two cats right next to each other, I don't see any problem fixing the problem of a plugged cat". He called it an "exhaust impingement" but however he put it, I am glad I got it done. Cost me $30.
User avatar
green02crew
Crew Elite
Crew Elite
Posts: 863
Joined: Mon Nov 12, 2007 7:56 pm
Location: Northern NH
Contact:

Post by green02crew »

Is a pre-cat required in NH? I called an inspection shop and they said no problem it doesn't matter if its gone. The other shop told me if it came with one, it must be there. I've tried to review the laws but its tough.

http://www.gencourt.state.nh.us/Rules/saf-c3200.html

There are the inspection requirements for NH.

It sounds like if it came from the factory it has to be on there, but then again it only says there has to be a cat installed nothing about the precat.
2002 S-10 Crew Cab
Too Many Mods Check the Readers Rides Page
User avatar
blks10
Crew
Crew
Posts: 50
Joined: Thu Oct 23, 2008 10:26 am
Location: Maryland

Post by blks10 »

I had that problem on my 98 2.2 s10. Came from the truck misfiring, and destroyed the cat with to much fuel in the exhaust. a new TPS and she was all fixed
I speaka da english
User avatar
green02crew
Crew Elite
Crew Elite
Posts: 863
Joined: Mon Nov 12, 2007 7:56 pm
Location: Northern NH
Contact:

Post by green02crew »

Is the pipe leading to and from the precat 2 1/2 ID or 2 1/2 OD?
2002 S-10 Crew Cab
Too Many Mods Check the Readers Rides Page
User avatar
HenryJ
Admin K Elite
Admin K Elite
Posts: 12705
Joined: Tue Oct 01, 2002 9:14 pm
Location: Ontario, Oregon
Contact:

Post by HenryJ »

Depends upon where you cut. The front is too close to that bend. Your best bet will be to measure yours, where you cut.
My guess is that the 2 1/2" pipe will need a little adjusting to fit properly.

Forgive my use of the word pipe. Tube would be more appropriate.
A pipe is measured and ordered from the manufacturer
based on its INNER diameter (ID).


A tube is measured and ordered from the manufacturer based on its OUTER diameter (OD).
A couple stainless steel compression sleeve clamps will put it back together temporarily if that is what you have in mind. I would expand both ends to slip over. The front side will be short and tight though. Easier to fix with the bender and expander close.

"Speed doesn't kill, suddenly becoming stationary does." - Richard Hammond
"Speed is just a matter of Money - How fast do YOU want to go?"-Mechanic from Mad Max-
If at first you don't succeed - Don't take up Skydiving!
- ThunderII KE7CSK
User avatar
killian96ss
Crew K Elite
Crew K Elite
Posts: 2669
Joined: Tue Sep 09, 2003 11:53 am
Location: Sacramento, California

Post by killian96ss »

green02crew wrote:Is the pipe leading to and from the precat 2 1/2 ID or 2 1/2 OD?
2-1/2" OD

Steve
User avatar
green02crew
Crew Elite
Crew Elite
Posts: 863
Joined: Mon Nov 12, 2007 7:56 pm
Location: Northern NH
Contact:

Post by green02crew »

Is it possible to gut the precat and leave it installed or is the material of composition that it would not easily come out? It does look like a tough spot to clamp on a straight pipe until summer where I can get under there and do it right with a torch.
2002 S-10 Crew Cab
Too Many Mods Check the Readers Rides Page
User avatar
roadrunner
Crew K Elite
Crew K Elite
Posts: 1267
Joined: Wed Dec 05, 2007 5:39 pm
Location: NW KS

Post by roadrunner »

green02crew wrote:Is it possible to gut the precat and leave it installed or is the material of composition that it would not easily come out?
If you make your cut after the pre-cat you could take a punch or short bar and hammer and break up the material that comprises the honeycomb inside the cat. You might want to take the Y pipe off to get better access after making the cut as it would be rather unhandy without being up on a hoist. If you do it this way just make sure you remove all pieces and debris as they would blow back into your main cat causing possible troubles there if you dont.
2001 CC LS, pewter, stock, 4.3,Wait4meperformance, CFM throttle blade, Helix throttle body spacer, 4spd auto, 3button electric 4x4 shift, heavy duty factory suspension, Bilsteins, 1" rear wheel spacers, skid plates.
User avatar
quickbiker
Crew K Elite
Crew K Elite
Posts: 1575
Joined: Fri Oct 11, 2002 6:01 pm
Location: VA
Contact:

Post by quickbiker »

I'm wondering now if my precat is going. I got the P0101 first time today. The MAF looks clean enough. :roll:
[size=75][url=http://outsideventure.com/s10crew/]01 S10 Crewcab - SAS'd[/url][/size]
HCO4x4
Crew Elite
Crew Elite
Posts: 163
Joined: Thu Jan 10, 2008 12:32 pm
Location: Vero Beach, Florida

Post by HCO4x4 »

I don't think the honeycomb can be broken that easily...I tried to do that after I cut it all off and couldn't crush it.
[size=75]-2001 s-10 crew - K&N intake, 2" PA body lift, tbar crank, bilstein shocks, 15" american racing baja rims, 31x10.5r15 bfg MUD terrains[/size]
User avatar
green02crew
Crew Elite
Crew Elite
Posts: 863
Joined: Mon Nov 12, 2007 7:56 pm
Location: Northern NH
Contact:

Post by green02crew »

If I do cut it off, I'll be cutting it as close to the precat itself to retain as much pipe as possible. In doing so, if the situation arose where it had to be reattached, could a good exhaust shop weld it back on? Assuming it is not too damaged.
2002 S-10 Crew Cab
Too Many Mods Check the Readers Rides Page
User avatar
F9K9
Mod K Elite
Mod K Elite
Posts: 6183
Joined: Sun May 30, 2004 12:26 pm
Location: London, Kentucky, United States

Post by F9K9 »

Cut it as close to the rear of the precat as possible. Tie the rest of the exhaust over and toss a rag in it. Bust out the honey comb, start the engine, and repeat if, needed. Get a cheap muffler patch kit and drive to the muffler shop and have them re weld it.
[size=75][b]"For those who have fought for it, [i][color=red]FR[/color][color=white]EE[/color][color=blue]DOM[/color][/i] has a taste that the protected will never know."
[url=http://www.naxja.org/forum/showthread.php?t=73349]GUIDE TO SEARCHING. [i] (Some of the forum software is different but, it has helped me a lot.)[/i][/url][/b]
[b]"Those who don't know history are destined to repeat it." Edmund Burke[/b][/size]
User avatar
roadrunner
Crew K Elite
Crew K Elite
Posts: 1267
Joined: Wed Dec 05, 2007 5:39 pm
Location: NW KS

Post by roadrunner »

F9k9 is giving you the straight of it Green. HCO4x4 is correct on the fact it doesn't crush easily but if you drive a pointed punch or bar into it it can be broken up and removed. If you make a cut with a saws all you will only loose 1/32 to 1/16" of pipe (width of the cut) and should be able to directly butt the empty cat back to the rear pipe at the cut and a shop with a wire-welder should not have any trouble welding it back together. After removal of the honey-comb material inspect the inside of the cat-shell to make sure there is no wire mesh remaining there. Remove it if it is there. Some manufacturers put a wire buffer mesh there to cushion the insides from the shell for expansion as well as possible impact damage.
2001 CC LS, pewter, stock, 4.3,Wait4meperformance, CFM throttle blade, Helix throttle body spacer, 4spd auto, 3button electric 4x4 shift, heavy duty factory suspension, Bilsteins, 1" rear wheel spacers, skid plates.
User avatar
green02crew
Crew Elite
Crew Elite
Posts: 863
Joined: Mon Nov 12, 2007 7:56 pm
Location: Northern NH
Contact:

Post by green02crew »

Looks like my new tools will be put to the test tomorrow :lol:
2002 S-10 Crew Cab
Too Many Mods Check the Readers Rides Page
User avatar
green02crew
Crew Elite
Crew Elite
Posts: 863
Joined: Mon Nov 12, 2007 7:56 pm
Location: Northern NH
Contact:

Post by green02crew »

Pre-cat didn't look bad. I guess my less than poor fuel economy is contributed to something else. I decided in the end to just cut the pre-cat right out and retained it if need be for future use. I put a straight pipe in it's place and clamped it on with brackets. Seems like a decent temporary fix, I say that now seems temporary always becomes permanent. I did spray it with some high heat paint to prevent rust as it is prone to eating any exhaust parts after one winter. The 2 1/2" OD fit perfectly although there was not much room to work with thats for sure.
2002 S-10 Crew Cab
Too Many Mods Check the Readers Rides Page
User avatar
roadrunner
Crew K Elite
Crew K Elite
Posts: 1267
Joined: Wed Dec 05, 2007 5:39 pm
Location: NW KS

Post by roadrunner »

Let us know how it runs now as well Green. Mine didn't "look" bad either but MAN it sure ran better!!! Mpg has been better afterwards as well.
2001 CC LS, pewter, stock, 4.3,Wait4meperformance, CFM throttle blade, Helix throttle body spacer, 4spd auto, 3button electric 4x4 shift, heavy duty factory suspension, Bilsteins, 1" rear wheel spacers, skid plates.
User avatar
green02crew
Crew Elite
Crew Elite
Posts: 863
Joined: Mon Nov 12, 2007 7:56 pm
Location: Northern NH
Contact:

Post by green02crew »

First initial feeling, it does not warm up as quickly, seems to start easier/quicker I don't know how it might be related but backpressure perhaps?? Runs maybe slightly better at WOT, idle is same. Mpg will tell in due time.
2002 S-10 Crew Cab
Too Many Mods Check the Readers Rides Page
HCO4x4
Crew Elite
Crew Elite
Posts: 163
Joined: Thu Jan 10, 2008 12:32 pm
Location: Vero Beach, Florida

Post by HCO4x4 »

I removed my actual cat a long time ago and now I want to put one back on. Will any cat work in reducing emissions or will it still throw a code if I put the wrong one on?
[size=75]-2001 s-10 crew - K&N intake, 2" PA body lift, tbar crank, bilstein shocks, 15" american racing baja rims, 31x10.5r15 bfg MUD terrains[/size]
User avatar
green02crew
Crew Elite
Crew Elite
Posts: 863
Joined: Mon Nov 12, 2007 7:56 pm
Location: Northern NH
Contact:

Post by green02crew »

Some people have had issues with aftermarket cats throwing codes on the s-series. I would say stock is the best if you still have it lying around it might as well go back on. If you do not, I can't give a straight answer on what would work.
2002 S-10 Crew Cab
Too Many Mods Check the Readers Rides Page
User avatar
Rockrz
Crew Elite
Crew Elite
Posts: 414
Joined: Sat Nov 17, 2007 7:18 am
Location: Texas

Post by Rockrz »

I'm thinking of having an "accident" with may sawzall and accidently cut that pre cat off altogether, and have a repair pipe wielded in.

Who needs a pre cat anyway? Image
[size=75]I'm drivin a...2003 Chevy S10 Ex Cab LS 2WD, Auto, 4.3L, Vin Code X[/size]
OpieOnCrack
Regular
Regular
Posts: 17
Joined: Mon Dec 01, 2008 10:11 pm
Location: Oklahoma

Post by OpieOnCrack »

Will it throw an error code if I remove both the Cat and Precat? I have sensors before and after the cats.

Let me know. I've got the pipe to replace, but don't want to stare at a code light forever.

Thx
User avatar
Rockrz
Crew Elite
Crew Elite
Posts: 414
Joined: Sat Nov 17, 2007 7:18 am
Location: Texas

Post by Rockrz »

If it does they have plugins for the O2 sensors that
makes the ECM "think" everything is working just
fine, eliminating any trouble codes.

Course, these things are probably illegal
I heard you could get 'em on eBay
[size=75]I'm drivin a...2003 Chevy S10 Ex Cab LS 2WD, Auto, 4.3L, Vin Code X[/size]
OpieOnCrack
Regular
Regular
Posts: 17
Joined: Mon Dec 01, 2008 10:11 pm
Location: Oklahoma

Post by OpieOnCrack »

Any idea what they are called. We really don't care much for law here in Oklahoma. lol
User avatar
Rockrz
Crew Elite
Crew Elite
Posts: 414
Joined: Sat Nov 17, 2007 7:18 am
Location: Texas

Post by Rockrz »

O2 cheaters, I guess...
[size=75]I'm drivin a...2003 Chevy S10 Ex Cab LS 2WD, Auto, 4.3L, Vin Code X[/size]
User avatar
HenryJ
Admin K Elite
Admin K Elite
Posts: 12705
Joined: Tue Oct 01, 2002 9:14 pm
Location: Ontario, Oregon
Contact:

Post by HenryJ »

There is really no need to delete the high flow cat that we have.

"Speed doesn't kill, suddenly becoming stationary does." - Richard Hammond
"Speed is just a matter of Money - How fast do YOU want to go?"-Mechanic from Mad Max-
If at first you don't succeed - Don't take up Skydiving!
- ThunderII KE7CSK
User avatar
YellowCrewCabber
Crew Elite
Crew Elite
Posts: 233
Joined: Thu Dec 04, 2008 10:03 am
Location: Franklin, Tn.
Contact:

Post by YellowCrewCabber »

I was wondering how many of you that have had problems with their cats and pre cats were using fuel addivtives? Fuel inj cleaner, fuel system cleaner, octane boosters, products like "Heet" or enven fuel stabilizers. Several years ago when I owned the Sonoma I would use additives mostly fuel injector cleaner. By the time I reached 90k on the truck I was having emission problems. A shop supervisor at a GMC dealer told me that the gasoline makers put enough additives in the fuel to keep the fuel system clean. My CC had 14k on it when I bought it. It now has 126k on it and I have not put any additives in the fuel and so far have not had a problem with anything fuel related. I am expecting the pump to go out any day now. :lol: I'm not saying that adding fuel additives are causing emissions problems just curious if it could be.
Jeff
[size=75]04 ZR5 CC

Xbox Live Gamer Tag-Gefke6367[/size]
User avatar
HenryJ
Admin K Elite
Admin K Elite
Posts: 12705
Joined: Tue Oct 01, 2002 9:14 pm
Location: Ontario, Oregon
Contact:

Post by HenryJ »

I am sure my precat was done in by testing the snake oil miracles.
Vararam, Bosch Plat +4, Granetelli MAFS, just to name a couple that may have contributed.

"Speed doesn't kill, suddenly becoming stationary does." - Richard Hammond
"Speed is just a matter of Money - How fast do YOU want to go?"-Mechanic from Mad Max-
If at first you don't succeed - Don't take up Skydiving!
- ThunderII KE7CSK
User avatar
roadrunner
Crew K Elite
Crew K Elite
Posts: 1267
Joined: Wed Dec 05, 2007 5:39 pm
Location: NW KS

Post by roadrunner »

Yeah, kinda funny though, the first thing that supervisor would likely do when you come in with a rough idle or similar problem is grab a bottle of injector cleaner. But then that would be okay cause after all it would be administered by "proper" personnel. lmao (translation for a proper price)
2001 CC LS, pewter, stock, 4.3,Wait4meperformance, CFM throttle blade, Helix throttle body spacer, 4spd auto, 3button electric 4x4 shift, heavy duty factory suspension, Bilsteins, 1" rear wheel spacers, skid plates.
fallvitals
Crew K Elite
Crew K Elite
Posts: 1132
Joined: Tue Mar 03, 2009 2:34 am
Location: Dunbar, WV
Contact:

Post by fallvitals »

huh, i was wondering what that thing was, i figured some kind of small cat but wasnt sure. Got me thinking about cutting it off too... (leaving the high flow cat).


On my old 97 4.3 2wd s10. Dad and i were flushing the coolant system, needed more anti feeze, when I got back the engine was horrible. spitting, sputtering, etc. Dad had sprayed the engine with the water hose to clean it some, apperantly water got somewhere it shouldnt have. :roll: I think he was revving it some, I was standing at the back and red hot pieces of junk came flying out of the tail pipes! :shock: I had him kill the engine, I was thinking he blew it up or something. We checked the distributor for water in it, none. the stuff cooled off, it was a honey comb like matterial, I had a magnaflow exhaust, so i knew it had to be from the cat. Probably unburnt fuel got in there. But when he started it up, it was noticably louder. And it started up and ran just fine after that. Not sure what the problem was.

I also got much better gas milage, went from about 215 to a tank to about 240 to tank IIRC. but that was pretty much all city driving too. But did did throw codes. I looked at 02 simulators, but didnt want to pay for em, I drove with that light on till the day I traded it, lol.


So, ill be the one to ask the dumb question, (though f9k9 said he got better MPG, it was a while ago, so maybe something has changed), by removing only the Pre-Cat, leaving the high flow cat in place, your gonna get a ltitle better MPG, and just a little more sound? right?

If so.. i might have to do that....
User avatar
F9K9
Mod K Elite
Mod K Elite
Posts: 6183
Joined: Sun May 30, 2004 12:26 pm
Location: London, Kentucky, United States

Post by F9K9 »

fallvitals wrote:........So, ill be the one to ask the dumb question, (though f9k9 said he got better MPG, it was a while ago, so maybe something has changed), by removing only the Pre-Cat, leaving the high flow cat in place, your gonna get a ltitle better MPG, and just a little more sound? right?

If so.. i might have to do that....
1. there are no dumb questions if, you have tried to search and apparently you have.

2. HenryJ and the muffler shop "guy" both said my precat wasn't bad.

3. While my mileage did increase slightly, I cannot point the finger at the precat, as the culprit.

4. I was experimenting with several things to try to cure my overheating issues. I "think" in retrospect that I had a bad VSC (Variable Speed Controller) for my efans.

The timing of the VCS replacement and the precat elimination was very close IIRC.

Nothing can be assumed through my particular situation. I wish we had a "cook book" to tell you if "X" occurs. you need to perform this "Y" mod.

Hell, Brule and I didn't stumble upon the bump stop answer to the marvelous mystery lift until we were racing against darkness at Moab last year. :lol:

No cook book for us or any other automotive enthusiast. :wink:
[size=75][b]"For those who have fought for it, [i][color=red]FR[/color][color=white]EE[/color][color=blue]DOM[/color][/i] has a taste that the protected will never know."
[url=http://www.naxja.org/forum/showthread.php?t=73349]GUIDE TO SEARCHING. [i] (Some of the forum software is different but, it has helped me a lot.)[/i][/url][/b]
[b]"Those who don't know history are destined to repeat it." Edmund Burke[/b][/size]
OpieOnCrack
Regular
Regular
Posts: 17
Joined: Mon Dec 01, 2008 10:11 pm
Location: Oklahoma

Post by OpieOnCrack »

K' I'll just cut out the pre-cat. I work at a tube and fence manufacturer, so tubing is free. lol Also got a Dynomax muffler, so know that my fuel tank is fixed, I'm not afraid to allow my friend under there with a welder...
\
Thanks for the advice
User avatar
LUVMY02CREW
Crew
Crew
Posts: 77
Joined: Wed Jul 18, 2007 2:03 pm
Location: Shelbyville, TN

Post by LUVMY02CREW »

I've been setting p0300 occassionally. Idle got progessively worse and I finally changed plugs, wires, dist cap and rotor 2 days ago with 97k on odometer. Still super rough idle. My local mechanic said probably the precat clogged, soooo...

I will probably cut it out tonight as wifey prepares for a yard sale so I can go first thing in morning to get "hole in exhaust" replaced.

I'm hoping for driveability again, because I haven't driven it since tune-up cause I didn't want to jack anything up with it idling so rough and the random misfires.
[size=75]ALWAYS pray for and expect the best, but be prepared for the worst! Life seems to operate a little smoother for me this way[/size]
User avatar
LUVMY02CREW
Crew
Crew
Posts: 77
Joined: Wed Jul 18, 2007 2:03 pm
Location: Shelbyville, TN

Post by LUVMY02CREW »

Well, after cutting out the pre-cat and going on a test run earlier, the truck seemed to idle a little smoother at stops.

My pre-cat looked like the pictures that f9k9 posted earlier. No clogging, but oh-well it's outta there now.
[size=75]ALWAYS pray for and expect the best, but be prepared for the worst! Life seems to operate a little smoother for me this way[/size]
fallvitals
Crew K Elite
Crew K Elite
Posts: 1132
Joined: Tue Mar 03, 2009 2:34 am
Location: Dunbar, WV
Contact:

Post by fallvitals »

HenryJ wrote:
killian96ss wrote:
2 1/2" on both ends. It only needs to be flared enough to fit over the 2 1/2" pipe. The cat is 3" in/out , but you would have to cut right up close to get it to that inside diameter.
Not to beat a dead horse, but before ordering, or going to advance to check first..

What I need to imitate Brule's set-up is this:

Image

A gasket for it,

and just some 2 1/2" pipe flared at one end?

Buddy of mine is gonna weld it all up for me :) Wanna make sure I have exactly what I need before he does this for me.

And another question.. Brule's picture... is there an additional peice of short pipe welded inbetween the Y and the flange? Looks like a new weld there, but old pipe?
User avatar
LUVMY02CREW
Crew
Crew
Posts: 77
Joined: Wed Jul 18, 2007 2:03 pm
Location: Shelbyville, TN

Post by LUVMY02CREW »

Just a quick follow up on mine...after cutting pre-cat out friday night, I took truck to local muffler shop saturday morning and they welded in new pipe no problem - $21.95 and I was out the door. I wasn't too concerned with the flange connection, but it does look like that would be the best way to go.

It didn't solve the Running Rough issue(mine starts about 7 posts down), but at least thats one thing in the future I won't have to worry with.
[size=75]ALWAYS pray for and expect the best, but be prepared for the worst! Life seems to operate a little smoother for me this way[/size]
User avatar
HenryJ
Admin K Elite
Admin K Elite
Posts: 12705
Joined: Tue Oct 01, 2002 9:14 pm
Location: Ontario, Oregon
Contact:

Post by HenryJ »

fallvitals wrote:...some 2 1/2" pipe flared at one end? ... is there an additional peice of short pipe welded inbetween the Y and the flange?
Pipe flared to fit at both ends. Yes there is a little piece slipped over the Y-pipe.

"Speed doesn't kill, suddenly becoming stationary does." - Richard Hammond
"Speed is just a matter of Money - How fast do YOU want to go?"-Mechanic from Mad Max-
If at first you don't succeed - Don't take up Skydiving!
- ThunderII KE7CSK
User avatar
hoggy
Regular
Regular
Posts: 11
Joined: Mon Jul 06, 2009 6:26 pm
Location: Hudson, WI

Post by hoggy »

My 02 CC did the same thing, no power, barely able to hit 50mph, ran like crap. I took a hole saw and cut a 3 inch circle into the bottom of the cat. Took a crow bar and busted all the ceramic stuff out welded that 3 inch circle i cut out back in. Truck was awsome after that except the check engine light came on. Then i orderd one of those o2 sensor bypass things from casper electronics (don't make them anymore). It's still running good 2 years later. I'm gonna be takin the precat out in a few weeks when i redo my exhaust.
User avatar
F9K9
Mod K Elite
Mod K Elite
Posts: 6183
Joined: Sun May 30, 2004 12:26 pm
Location: London, Kentucky, United States

Post by F9K9 »

Man, I would love to be able to weld. Would save allot of hassle for me. I would just worry about MILs and luckily you got the O2 "foolers" before production ceased.
[size=75][b]"For those who have fought for it, [i][color=red]FR[/color][color=white]EE[/color][color=blue]DOM[/color][/i] has a taste that the protected will never know."
[url=http://www.naxja.org/forum/showthread.php?t=73349]GUIDE TO SEARCHING. [i] (Some of the forum software is different but, it has helped me a lot.)[/i][/url][/b]
[b]"Those who don't know history are destined to repeat it." Edmund Burke[/b][/size]
User avatar
hoggy
Regular
Regular
Posts: 11
Joined: Mon Jul 06, 2009 6:26 pm
Location: Hudson, WI

Post by hoggy »

Welding is pretty easy, but I got a millermatic 250 with .35 wire. It's a real nice machine. Got it real cheap, the only thing it didn't come with was the aluminum spool gun which was burned in a shop fire. When ever my buddies need something welded they all come to my house.

I gotta watch where i go with that simulator. I have it attached to the outside of my frame rail and there's a red light that flashes sayin it workin. I call it my bomb :lol:
I wonder how hard they would be to make, one of these days when i'm bored I'll have to crack the case open and see whats inside.
User avatar
F9K9
Mod K Elite
Mod K Elite
Posts: 6183
Joined: Sun May 30, 2004 12:26 pm
Location: London, Kentucky, United States

Post by F9K9 »

hoggy wrote:Welding is pretty easy...............
Shut up until you do a search about "ducks" and "waterfowl"! with me as the author! :schwing:
[size=75][b]"For those who have fought for it, [i][color=red]FR[/color][color=white]EE[/color][color=blue]DOM[/color][/i] has a taste that the protected will never know."
[url=http://www.naxja.org/forum/showthread.php?t=73349]GUIDE TO SEARCHING. [i] (Some of the forum software is different but, it has helped me a lot.)[/i][/url][/b]
[b]"Those who don't know history are destined to repeat it." Edmund Burke[/b][/size]