I have a 93 Chevy 1500 with 350 ci, auto tranny--I've had this problem for about a year. Say for instance I'm in a parking lot and I pull out of a space, when I hit the gas and let off, my truck starts to idle really low and stumbles and sounds like it's about to die. It never does die though, it just comes back to idle. If I'm going about 35-40 mph and barely have my foot on the gas it jerks back and forth like it's running outta gas, but when I'm on the gas at regular throttle it does fine. I've changed plugs, rotor, cap, fuel filter, even used Sea Foam through the vacuum line in the brake booster to clean it all out. The throttle body is clean and so are the bowls. The engine runs strong under heavy acceleration and is not missing otherwise. So, I'm lost and don't know what to do now....can any of you guys help me out???

By the way, I've been told that it might be the coil, idle air control valve even the EGR valve. I do know that none of these parts have been replaced, they are all original parts. Thanks!!!!

 

egr. clean or replace.

 

Mrnapolean, ok I'll try that and see what happens. I always thought it maybe a loose timing chain but it doesn't make the noise where it slaps against the timing chain cover. I didn't know that the chain could actually jump like that.

 

I would check all vaccum lines first! Second I would test the IAC motor.

 

We were having a similar problem with our 93 suburban. Everyone told us the same as the comments you have posted before mine. We went through timing and vaccum troubleshooting, and everything was fine. It was the stupid MAP sensor. Makes sense now. Let us know what the problem was.