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Tough trouble

r2142

By r2142
in Ask A GM Technician

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r2142 Enthusiast

r2142

Posted
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I am at my wits end. I own a 1997 C1500 Silverado extended cab and I have just rolled past 210k miles. I wish to keep the truck since I cannot find the money to buy a new one so I have been repairing and replacing as necessary, which brings me to my issue.

 

I have owned the truck for 3 years and bought it at 160k miles and at the time it had some issues with it in the engine as it didn't idle just right and it choked up on hard acceleration so I replaced all the usual and got my power back but the truck always had a bit of a stumble that never went away. I replaced nearly every part that deals with ignition and timing and got to the point this January that I had enough money to pay someone to rebuild an engine for me and pulled the original engine and dropped in the new one (rebuilt).

now the fun part, the stumble issue showed up in the new engine as well. I have paid two different shops to diagnose and bother cannot find the issue in why it is misfire. The kicker, is all the misfires occur in just the front of the engine in cylinder 3 (the worst) and 2 and 4. The other cylinders do not misfire and the miss is visible at idle and can be felt at any throttle while driving.

The parts from the old engine were transferred to the new engine

normally I would have assumed the issue was in the spider injector but it passed leak down test flawlessly.

 

One more issue is it would seem that the computer is trying to cut fuel and the truck is running slightly lean.

 

I am currently considering that even though the EGR test passes it may be possible that there is something wrong with it opening too far and messing with the front cylinders.

 

Any assistance anyone who has an idea would be greatly appreciated.

Thanks in advance

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Jsdirt Senior Enthusiast

Jsdirt

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This sounds similar to a nightmare '96 Tahoe I worked on. No matter what was replaced on it, we have severe misfires in 2 cylinders, and a random misfire in a 3rd - seemed to be the rears in opposing banks in this case. I suspect the junkyard sold me a V6 computer, because the guy was totally uncooperative, even though I was still within their 90-day warranty. He demanded a dealer receipt for the troubleshooting. I almost punched him in the face ...

 

My buddy sunk so much money into this thing, we gave up. He's been driving it the past 2 years on occasion running on 6 cylinders. Gets about 7mpg. Friggin horrible ...

 

Still no closer to a solution. Only thing I can do from this point forward is chance another computer. Stupid electronics. Nothing needs to be this damn complicated ... :banghead:

Jsdirt Senior Enthusiast

Jsdirt

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Need to find someone who specializes in drivability issues on OBD-II vehicles. Sounds like the local shops aren't that well versed in that particular repair segment.

r2142 Enthusiast

r2142

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Broke down and decided to take to a dealership they wasted time and time money to not solve the problem. They ran an injection cleaning motor vac with slight improvement but not solved.

r2142 Enthusiast

r2142

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Took to another dealer with a good reputation and they say it is the Injection Spider may be faulty but I am not going to give them $1100 for something I can do for $400

Jsdirt Senior Enthusiast

Jsdirt

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One of the worst GM designs in history, besides the diesel 350 of the 70's-80's.

grampadirt Senior Enthusiast

grampadirt

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I did the MPFI upgrade on my wife's '99 GMC Suburban almost five years ago,best thing I ever did for it.The local dealership diagnosed the CFI fuel control module under the upper plenum took a crap.It's really not that hard to do.

Jsdirt Senior Enthusiast

Jsdirt

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Didn't know that existed - that's the way to go right there! That spider assembly has got to be the biggest steaming pile of engineering in automotive history.

 

Surprised they didn't located it inside the oil pan .... :freak:

grampadirt Senior Enthusiast

grampadirt

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I did a ''how to'' thread on another site,it may help shed some light on the MPFI upgrade.

 

http://Well I'll Be Damned,Wifey's Burb Is Alive(How To,Kind Of)

 

 

 

btw I'm dirtyoldman there :jester:

Jsdirt Senior Enthusiast

Jsdirt

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That link brought me right back this thread .... just FYI.

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