hey guys i know that this isn't a thirdgen topic, but this is the best place i can think of to go for this problem, and seeing as how the two ecm's may be similer i thought someone here may have some advide.

anyhow i have a 91 gmc light 3/4 ton and it has an idle problem. sometimes out of the blue it just up and dies. it kind of sputters (actually it tries to run but the revs just go down, then up a little, then down a little more then it finally dies) i try to give it gas when it does this and it does no good whatsoever. and when it finally does die it is pretty reluctant to start again, you relly have to crank it a lot.

the air filter was dirty, i cleaned it out really good (haven't gotten around to getting a new one yet) it seemed to help a little, but it still dies just not as often.

sometimes it runs a little hotter than normal, but not every time. idk if that is related to the problem or not.

this has a crate 350 which is a 350 caprice tbi replacement engine, but the same old 5.7litre intake, tbi etc that came on it.

i think it is some little computer controled widget, but i am not sure. vehicles that are more computer that car aren't really my forte`

so anyone have any suggestions?

i really appriciate the help, thanks a lot.

 

Obviously a violation of the board rules in the strict interpretation sense.

But, I'll let the TBI guys decide if there's enough "3rd gen related"-ness to this to let it live.

 

I will only let it stand because many people use 350 TBI's from trucks and have problems with them once they are installed. They are no different than their little brother so diagnosing them helps everyone to an extent that uses or is considering use of this motor. As soon as this thread strays from TBI related problems I will zap it.

Ok, now onto your problem. When was the last time it had a tune up? A fualty 02 is usualy the culprit for the symptoms you describe. How does the motor run cold?

 

cold the beast runs fine, not a single problem one.

again, i really am sorry for putting this here, i know this isn't the place for it, but i didn't know of any other boards where i could go. i could have found a new board but i used to spend a lot of time on this site so i knew that many of the people here knew something, thanks for helping me out, you have no idea how much i appericiate it.:hail: :hail: :hail: :hail: :hail: :hail: :hail:

 

Since the motor runs fine cold I would focus on the 02. When the car is cold is does not take any readings from the 02. It is in open loop and will not use the 02 until it heats up and goes into closed loop. When it goes to get valvues from it it is not working, hence your problems.

 

well today i'm gonna see if i can get an o2 for it, thanks a bunch for the help

 

ok, i got the o2 sensor, but it didn't seem to help, what now? i heard that som ecomputers need some time to adjust... think that may be the case?

if no tthe o2 then what else may it be?

thanks again guys

 

I would run some simple tests with a voltmeter on your pick up coil, coil, and CTS sensor. Values for what they should read when opporasting correctly can be found in any haynes or chilton. What is the condistion of the plugs and wires. Something as simple as a set of old plug wires can cause havoc. Might want to check the resitance on those as well while you have that volt meter out.

 

Sounds alittle like a lean surge. I would have someone check your fuel presure just to rule out a fuel pump (pressure) related problem.

 

If you want to test your fuel pressure on trucks like ours, go to Autozone and they have a gauge with an adaptor that can go inline and you can just screw the gauge on whenever you need it. It is made by Actron and costs about $35.