Problem with a Chevy, looking for an expert...
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Hall Of Fame
Joined: Jan 2004
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Problem with a Chevy, looking for an expert...
trying to fix Jr's truck as it doesnt want to run right... when the we got it, it ran perfect. Sat for a month or so then fired it up and it ran like crap. took it fora spin and it acted just like a bad fuel pump, surging as if it was starving for fuel. So here's what we've done to it...
new fuel filter,
checked fuel pressure under load...( in gear with some throttle) sits at 12.5 psi, range is 9-13psi.
take a peek at the injectors and the appear to be working.
checked all the vacuum lines for leaks, none.
then I went to set the timing and yank the connector that i'm instructed to and fire it back up and it purrs like a kitten, idles perfectly. verify the timing and it's good, plug the timing wire back in and runs like crap again. so I think the ignition module might be bad and swap it out... nope, same problem.
Now i'm thinking it could be a ECM (PCM) problem or one of the inputs to it. As of now there are no CE lights and I have not checked it for any codes yet (just found out how last night).
So has anyone here run into this on a Chevy 350 before? year is 1991 1/2 ton truck, TBI motor
new fuel filter,
checked fuel pressure under load...( in gear with some throttle) sits at 12.5 psi, range is 9-13psi.
take a peek at the injectors and the appear to be working.
checked all the vacuum lines for leaks, none.
then I went to set the timing and yank the connector that i'm instructed to and fire it back up and it purrs like a kitten, idles perfectly. verify the timing and it's good, plug the timing wire back in and runs like crap again. so I think the ignition module might be bad and swap it out... nope, same problem.
Now i'm thinking it could be a ECM (PCM) problem or one of the inputs to it. As of now there are no CE lights and I have not checked it for any codes yet (just found out how last night).
So has anyone here run into this on a Chevy 350 before? year is 1991 1/2 ton truck, TBI motor
Grand Champion
Joined: Feb 2007
Posts: 5,704
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From: Warminster, PA
RE: Problem with a Chevy, looking for an expert...
have you gave it a basic tune up? sometimes the wires could be on in the wrong firing order and it will surge like that... but then again it would do it all the time... hmm.. thats a good question
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RE: Problem with a Chevy, looking for an expert...
everything was fairly new when we got it... we did swap cap & rotor, ohmed out all the wires and re-gapped the plugs. if it was a tune issue, it would still run like crap when you yank the timing wire so i'm going to go see if there are any stored codes shortly and go from there.
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RE: Problem with a Chevy, looking for an expert...
well we checked all the grounds, wiring back to the pcm & swapped out the pcm with a known good one... (just to add to what we did earlier...)
tonight we yanked out the dist to change the pickup coil and the pickups in the dist were broken & cracked... 1 of them we found under the distributor and another broke off when we yanked the distributor... we'll be getting one tomorrow to swap in... I'll let you guys know how it goes.
thanks for all the input!!
tonight we yanked out the dist to change the pickup coil and the pickups in the dist were broken & cracked... 1 of them we found under the distributor and another broke off when we yanked the distributor... we'll be getting one tomorrow to swap in... I'll let you guys know how it goes.
thanks for all the input!!
