slug

[dettony]

Ok so I have had this problem since I have had this truck its a 2003 crew cab 123,000 just had the trans flushed thinking that was my problem but its still there I have to pretty much mash the pedal to go on my truck not all the way to the floor but u get the idea its a slug I don't know if that's the way these trucks are or what could it be my cat plugged or something I almost hate to drive it sometimes any suggestions would help it shifts fine all through the gears I just have to get on it going up a hill or taking off HELP

[HenryJ]

A few more details please.

Tune up status: Plugs, cap, rotor, wires, fuel filter, air cleaner, fuel injector cleaner. Any replaced parts.

Fuel grade and type.

Gearing and tire size.

Modifications.

Normal payload.

Location, terrain, altitude.

Do you have a precat?

[dettony]

I have not changed the plugs or wires since I have owned it. It has stock air filter no other engine mods. Always run premium gas 93 oct. 235/75/15 tire size stock drive train. No other mods I don't haul any thing I live in ky so there are lots of hills but its even on a straight path and I do have both cats on there

[HenryJ]

Try dropping to a mid grade fuel. 93 octane is not helping with out a change in timing. Read the thread explaining octane. 93 octane is not cleaner and does not produce more power. It is harder to ignite.
Use a fuel treatment every other engine oil change. Too much is as bad as never.

Time to look over the ignition system closely. A new set of wire, plugs , cap and rotor are in order.

Change the fuel filter now and every 20k miles.

I will assume that your tire size is the same it came with. That is the optional offroad tire that came with the 3.73 gears. The lower gear will help it jump out of the hole a little better.

Suspect the cat. A good muffler shop can drill test ports and check for pressure variance before and after. You can also use an IR thermometer to check for proper function of the cats. There should be a significant temperature increase post cat. 100 degrees differential is fairly common. Some common symptoms of a plugging cat include quiet exhaust with egg smell. Loud intake sounds at full throttle. Bogging performance. Warming up quicker than normal , especially when pushing it hard.
The precat can be deleted with no ill effects. The main cats have been pretty good and should not need replacement.

Think about installing a cat back for a little "oomph". It will wake things up pretty nicely. The stock muffler really is very restrictive. There is a reason they are so quiet.

Start with the easy stuff first. It is tune up time.

[s10 again]

HJ nailed it down pretty good. I would add that you might should do a coast down test to check for anything that might be dragging thus slowing down your acceleration. Simply find a good level road and bring your truck up to 55-60 MPH. Then take your foot off the gas and shift into neutral. If you loose speed very quickly something is dragging.

By the way how has your MPGs been as that can be a clue as to what is going on.


Chris.

[dettony]

Mpg 12 to 15 if I'm lucky can u take out both cats and just put pipes there wirh no check engine light coming on and I guess ill get the pulgs and wires changed any other suggestions let me no thanks guys

[HenryJ]

15 mpg will likely be the best you can do. I am saddled with 10% ethanol here and it pushes hard to get 15 mpg around town on that stuff.

Dragging brakes could be something to look at for sure. Watch those darn sticky slide pins.

The main cat needs to be there for the light to remain dark. It is not a bottle neck anyway as it is a 3" high flow design. They don't get better than that.

Look the plugs over carefully as well as the cap. The evidence with tell volumes.

[s10 again]

I don't thing we can ditch the main cat without modifying the signal on the rear o2 sensor. As HJ said though you won't see much if any gain in deleting it unless it is plugged. However the pre-cat is another story. How does your MAF screen look?

Chris

[dettony]

What is the maf and also how about your trucks are the peppy or dogs like mine? Is it because they are heavy trucks? I had a 96 blazer and I didn't remember it being a t##d

[roadrunner]

MAF= mass airflow sensor. Located in the air intake pathway between the air cleaner and the throttle body. My truck has the higher gear ratio and 235x75x15 tires and is no slug. Had trouble previously with loss of power but pre-cat-ectomy cured that. Definitely woke up that sleepy little V-6. My mileage is correspondingly better as well due to higher gear ratios. 20-23 highway and 14-16 city. We won't talk about when wheeling in the mud though as it gets pretty thirsty there. That's to be expected though. More power required=more fuel used=poor fuel economy.

[s10 again]

Well compared to my 99 reg cab Extreme my crew is a bit doggy.

But I would not call it slow either. Once you are sure there is nothing wrong like fuel filter, tune up, restricted cat, something dragging or other things. Then there are things that can be done to help with the giddy-up go.

And the MAF= Mass air flow sensor. It is inline on the intake tube between the air filter and the throttle body. It has a screen on it to protect it from debris and if air filter has not been changed properly that screen can get dirty restricting air flow.


Chris

[dettony]

I will check the screen tomorrow and if the pre cat was plugged would it even run at all? I know its not a hod rod but I think it should be a little more peppy than it is

[HenryJ]

I will check the screen tomorrow and if the pre cat was plugged would it even run at all?

Get a can of cleaner for the MAFS.
A plugging cat will still run. How fast depends upon how plugged.

Clean out the throttle body too. Once all this tune-up stuff is done , reset the PCM. That will load the new cold start parameters.

[s10 again]

Fuel filters , clogged cat and restricted intake air can all act much the same way early on. All can have a major effect on acceleration. Our modern computers will adjust air/fuel ratio to attempt to keep the engine running as best it can. However that often means it will sacrifice performance if it needs to. where in the old carb days the engine might not have been able to run at all.

An example of this is a clogged air filter on a carb engine if left unchecked would carbon up the plugs and clog the cat till the engine could not run. But an EFI engine the computer will adjust A/F ratio to keep the carbon build up to a minimum. But the cost will be a major dent in performance as the computer starts cutting back the fuel to match the air it is getting. Same for exhaust if the computer senses a restriction as A/F gets out of whack the computer dials back the fuel. This keeps you going but not quickly.

My step father recently had a problem with his Z71 it ran smooth but lost a ton of power. It would take flooring it just to top some of the bigger hills here. He took the truck to have it looked at where they decided to replace the cats all 3. Afterwards the truck ran the exact same. Turned out that fuel filters are not good for 230k who knew . 10 bucks later the truck was running like new.This is why HJ suggested a good exhaust shop with the ability to check the cat for problems.

While on fuel filters, If your fuel filter has not been changed since you have owned the truck that would be a cheap starting point even if it is not the problem now it is counting down to being one at some point!!!

Chris

[killian96ss]

With 123k miles you should also replace both pre-cat 02 sensors. GM claims they are good for 100k miles, but in reality they are losing efficiency by 80k miles. Stick with AC Delco 02 sensors because some aftermarket brands like Bosch can cause surging problems and mpg loss.

Steve

[dettony]

Well I haven't had a chance to check that stuff out but I called the local muffler shop and they said 100 bucks to cut the resenater and put a pro flow on is that a good price? And is any one running a pro flo just curious how they sound?

[HenryJ]

I would do the tune up stuff first.

[dettony]

How hard is it to get to the plugs and wires can I do it myself or should I get a price on getting it done?

[s10 again]

Ditto on tune up first.

I have not done a plug change on this gen truck yet but does not look bad. When I do my plugs I will try going in through the flap in the wheel well I think.

Once you get to the cap and rotor read the tread about it on here first!!! The distributor body is plastic and special precaution needs to be taken.

Don't forget that fuel filter in the tune up. If it does not pick up a lot next I would go after those o2 sensors Steve brought up.

Chris.

[dettony]

I Will start checking it out tomorrow of the weather holds out but. Who knows !!!