I'm trying to reach GM TECH or anyone who can help me with this problem. The car has a rough excelleration stumbles on bottom end and steady popping through exhaust on upper end. The car has compleatly new electrical and firing system components. Has new fuel pump injectors where removed and cleaned timing chain is new and dist is new. It now stalls as soon as you put it in reverse. It has sit for about a year and a half being cranked once in a while. It is really driving me nuts HELP please.

 

Ok so I've gotten the O2 sensor changed and it is running somewhat better. Not popping all the time but still have a intermittent pop in the exhaust, pulls good in first gear but sluggish in 2nd then better in 3rd. Timing is reset still can't find any vacum leaks. Cleaned the IAC and Tweaked the TPS. Is there anything other than the MAP sensor that I have missed? Got to get more money for the MAP.

 

I am working on one with the same problem.
I have done everything you have done and more.
I am going to pull the engine now and check for a bad valve.

 

I feel for you this is driving me crazy have never had one this hard to fix. I've been working on cars for 44 years and this thing has me stumped. Is your transmission shifting right or sluggish? Mine is sluggish in 2nd till I get to 35 mph then picks up again.

 

It's a manual 6 spd.

 

Ok so as of now I have checked the fuel pressure and it's good but when I removed the fuel filter the fuel came out brown like chocolate milk. so even though when I replaced the fuel pump a while back and cleaned the inside of the tank now there is rust. Haven't had a chance to drive to see if it fixed the problems but it sure revs better and smoother. So I'll probably have to go a head and change the tank and sender and new pump don't want these problems again for a long time since the car will be going to my oldest grandson next year. He just go his learners Tuesday so now he wants to drive it. I told him I had to get it running better first. So thanks for all the help guys.