I have a 1988 Chevy truck with the 5.7 TBI with 125,000 miles on it. It starts OK and idles with a slight roughness. At all RMP is seems to burn too much fuel as indicated by a white, strong smelling exhaust.

From idle, when I advance the throttle slightly, the engine will begin to choke and die, but if I continue to advance the throttle it will pull out of it and run smooth again. (This only occurs after a short warm up. When cold , it will advance smoothly) I can bypass this by advancing the throttle quickly, though I sometimes notice hesitation. When the engine is fully warm, it will occasionally die while idling or after being shifted into reverse. It has always started right back up. There is an inconsistent miss at idle speed that sometimes appears at higher RPM.

I had the compression checked, and that is good. The Plugs, and wires are good, and I have replaced the distributor cap and rotor. I have replaced the egr (the person who owned it before me had capped the vacuum line to it). I tested the coolant sensor it is seems to perform fine. About 5.6 K Ohm at approximately 40 degrees and about 750 ohm after idling for a while. I checked the resistance of the tps but have not yet checked the voltage.

I thought it could be the Idle air control so I have one of those on the way, but that does not really explain the rich running after idle. I have not changed the oxygen sensor.

Any other thoughts on this? I am mostly concerned about it dieing at idle. If I can fix the rich mixture, that would be great, but I really hate when it dies at stoplights.

 

Your vehicle isn't a 3rd gen f-body, so your question doesn't belong on our Tech forum.

I'm moving it to the TBI forum because it may have some applicability to 3rd gen TBI systems. I'll let the moderators on the TBI forum decide if it is appropriate to discuss here.

 

My 94 van is a 5.7 tbi. I had a issue about 8 years ago where it would bog down right after a fuel fill up. A GM friend suggested I check the charcoal canister. Never did because I could never figure out how to get to it. Somewhere along the line the issue went away.
So you might check the canister and lines and you might try replacing the fuel filter.

 

He's posting it here because the truck forums for his vehicle tell him our website has some of the best TBI knowledge being that most of us want to make our cars perform better. On that note, it is very possible it is the Idle Air control motor. But im not one of the great techs on the board so I cannot make them post to help, sorry.

 

Yup, that's why I'm here: have truck & love Fbod's. All the truck sites I've looked into (at least 6) recommend this site, why, because you know this stuff better than anybody.

Whenever I have a question, I come here first. Someday, I hope to contribute some knowledge, bty, my truck has similar problem.

 

Exactly. Most of what I have learned about this motor came from these message boards.