loss of engine power.

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loss of engine power.

Postby RebelKid1822 » Fri Oct 18, 2013 8:28 am

howdy,

2003 zr5 4.3 175k
okay i have a loss of engine power. the truck has lost its get up and go, and seems to have no balls. i have changed a lot of parts and done a lot of tests and am now stumped. it has a newer fuel pump in it. no codes. newer tune up. brand new y pipe and cats. i've done compression tests, ohms tested the injectors, vacuum guage tests, fuel leakdown tests, and other things. im woundering if it could be a stretched timing chain? i have smooth idel and acceration. the power loss is more noticeable when i am climbing a hill or towing something. anyone got any ideas of where to head next?

thansk.
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Re: loss of engine power.

Postby F9K9 » Fri Oct 18, 2013 4:38 pm

Fresh fuel filter?
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Re: loss of engine power.

Postby AVTekk » Sat Oct 19, 2013 2:46 pm

Any way to get a hold of a nice scan tool and watch the O2 and fuel trim under load?
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Re: loss of engine power.

Postby RebelKid1822 » Sun Oct 20, 2013 5:23 am

i have watched the o2 sensors and fuel trims with a big boy scanner. everything worked normal. i grabbed a new fuel filter on my way home last night, the truck is about due for one, the filter on it has about 11k on it. i dont believe this is my issue due to the good fuel pressure and good fuel leak down test, but i do believe in ruling out the basics first. ill keep you guys posted.
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Re: loss of engine power.

Postby RebelKid1822 » Fri Oct 25, 2013 6:03 pm

howdy all,

i have replaced the fuel filter and did a flow test on the fuel pump. i also retimed the engine and checked the distributor drive gear for wear- simply because it was an easy thing to do. still no answers as to why i have such a power loss. anyone have any other ideas of things i can check? just to recap the truck idles and revs up fine, it has a loss under load. for instance today while driving it i have a hard time getting to 60mph, forget about maintaining any speed over that. when going up a hill you can here the motor load up. any help would be great!
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Re: loss of engine power.

Postby AVTekk » Sat Oct 26, 2013 7:17 am

Any way to check timing under load? Perhaps the ecm is pulling a lot of timing out for some reason. But 175k on the chain is a lot of miles, theyre pretty stretched after 100k.
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Re: loss of engine power.

Postby RebelKid1822 » Sat Oct 26, 2013 10:33 am

I'm having a friend run it on a dyno for me. Hopefully this will tell me whats going on.
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Re: loss of engine power.

Postby killian96ss » Sat Oct 26, 2013 3:19 pm

Make sure the MAF and IAT sensors are clean. I would also check the IAC valve and TPS for correct operation. Make sure the TPS has a smooth linear output and that it reaches 4.5 volts at WOT. Do you have any pending codes stored that haven't turned on the CEL yet? What spark plugs are you using? Have you tried swapping in a different coil? Are your O2 sensors new or original?

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Re: loss of engine power.

Postby RebelKid1822 » Sat Oct 26, 2013 5:49 pm

Newer clean map sensor.I will check the tps. No codes. No pending codes. Right now there are double platinum quad tipped plugs in it. With roughly 30k on them. 2nd o2 is newer. Other two are original- none were super carboned up. I put them into my new y pipe. I have not swapped the coil because I don't have a physical misfire or see any misfires happen with my scanner.
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Re: loss of engine power.

Postby HenryJ » Sat Oct 26, 2013 6:38 pm

Ditch the quad tip plugs. Too much flame shadow. Swap plugs to the Autolite irridium XP and check the coil for leakage. Try the hairspray trick on the wires, cap, and coil.

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Re: loss of engine power.

Postby RebelKid1822 » Sat Oct 26, 2013 6:42 pm

Ok. Ill give it a shot.
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Re: loss of engine power.

Postby killian96ss » Mon Oct 28, 2013 9:46 am

HenryJ wrote:Ditch the quad tip plugs. Too much flame shadow. Swap plugs to the Autolite irridium XP and check the coil for leakage. Try the hairspray trick on the wires, cap, and coil.

Even if the plugs are not the source of your current problem I also highly recommend the Autolite XP plugs. Almost all of the fancy 2, 3, and 4 electrode plugs out there cause problems in GM engines like loss of power, surging, reduced gas mileage, etc. Do not believe the advertising hype that these companies try to sell you. I have tried several designs over the past 25 years and have found that GM engines run best with believe it or not OEM plugs. AC Delco platinum, double platinum, and Rapid Fire are all very good plugs. The Autolite XP's have been my favorite plugs for a while now and work great in the 4.3L and many other GM engines. I run them in my 96SS, 88 S10 Blazer, and my 05 ZR2. I put these plugs in my 05 Z around the 25k mark and just checked them about 1k miles ago at 148k when I was going to replace them and they still looked great so I left them in. That's 125k miles of use and they still work just fine! I have also had an MSD street fire ignition firing those plugs for at least the past 100k and yet they have held up fine.

Back to your problem. Are you having a loss of power above a certain rpm or does your problem only happen when the engine is under a load? The reason I ask is because I've seen and heard of similar problems that actually turned out to be the transmission or TC starting to fail. When your TC clutches start to fail you will feel more slippage in the TC which can feel like a loss of power. Even worse is when the transmission clutches start failing which really feels like a loss of power especially when under a load which is when it will slip even more. Just thought I would throw that out there in case your problem has nothing to do with the engine. A stretched timing chain can cause a loss of power, but from my experience the engine will also run very rough and set codes. I'm right behind you with 150k miles and my 4.3 runs as strong as the day I bought it and it still has the original timing chain.

Steve
2005 ZR2 Blazer / Mods- Spectre CAI, Descreened MAF, Shaved Throttle Blade, 31" Goodyear Kevlar MT/R's, Black Rock Rims, MSD Street Fire CDI & Super Conductor Wires, Accel Cap, Rotor & Coil, Flowmaster 30 Series, Gibson Tailpipe, ES Bushings, Goodridge Brake Lines, Power Slot Rotors - 1996 Impala SS / Mods- Too Many To List - 1988 S10 Blazer / Mods- Too Many To List - 2001 S10 Crew Cab 4x4 / Mods- Too Many To List *Wrecked 12/06*
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Re: loss of engine power.

Postby RebelKid1822 » Mon Oct 28, 2013 12:02 pm

The power loss is under load, the rpms climb, but it takes forever to get to 60mph without redlining it. Last night I had to drive up a small front yard that had a hill. The tires did not spin, but the motor bogged way down I was in 4x4 and I did not think I was going to climb the hill. I will be changing the plugs and wires out soon.
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Re: loss of engine power.

Postby AVTekk » Mon Oct 28, 2013 12:14 pm

Ya I agree with the plug swap, Ive never had any luck with anything but ACDelco.
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Re: loss of engine power.

Postby RebelKid1822 » Fri Nov 01, 2013 9:02 am

howdy guys. two days ago i was fixing an exhaust leak on my s1o and had it on a lift. i found that two of my brake calipers were locked up, and that my clutch fan was bad. i am going to fix these problems tonight first before moving on.
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Re: loss of engine power.

Postby HenryJ » Fri Nov 01, 2013 9:31 am

Those could definitely be contributors :thumb:

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Re: loss of engine power.

Postby RebelKid1822 » Fri Nov 01, 2013 9:40 am

thats what im hoping. hopefully this will solve me issue.
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Re: loss of engine power.

Postby RebelKid1822 » Tue Nov 05, 2013 10:08 am

OKay good news. The truck is back to its old self. Four new calipers and a clutch fan. The fan was my biggest issue. I couldn't turn the old one at all, it was completely locked up. Thanks everyone for all the help.
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Re: loss of engine power.

Postby bagged sonoma » Thu Mar 27, 2014 6:00 pm

Just curious what calipers did you purchase for the rear? Thx
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Re: loss of engine power.

Postby RebelKid1822 » Thu Mar 27, 2014 7:37 pm

I just got all my calipers from autozone.
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