Car stumbles, dies upon acceleration

[greekguy7]

I have an '88 Pontiac Grand Prix with a 2.8litre V6 and auto trans. The car starts well, idles ok and runs ok when cold. Once it warms up and I try to accelerate normally from say 20MPH to 30MPH the car would stumlbe badly to the point that if I dont let off the accelerator it will stall out and die. It will restart immediately though. If I immediately let off the gas, it will keep running.

I replaced the TPS sensor and adjusted it for .55V at idle, and did idle relearn a couple times. The plugs, wires, filters, etc. have been changed in the last 10k miles. No codes either. The car has not been driven regularly for the past year partly cause it would do this sometimes, and partly cause it would die at idle in the past sometimes. The gas is new as I have been trying to get it to run right for the past few weeks. Any ideas or suggestions?? THANKS!!

[laveryt]

Kinda sounds like the fuel filter to me. Has that been changed ever?

[tractorman]

Yep, a fuel filter or fuel pump would be my guess. Better check that pressure.

[FastGT31]

my car did the same thing when i first got it, its a 3.1 but its basically the same. i changed the plugs myself and used champions (big mistake) and once i swapped them out for ac delcos the thing ran perfect from there on. i dont know which spark plugs you used but you cant go wrong with the delcos

[FastGT31]

my car did the same thing when i first got it, its a 3.1 but its basically the same. i changed the plugs myself and used champions (big mistake) and once i swapped them out for ac delcos the thing ran perfect from there on. i dont know which spark plugs you used but you cant go wrong with the delcos

[greekguy7]

The fuel filter and plugs were changed about 10k miles ago. The car has not been driven on a daily basis for about a year and a half but I did go thru all the old gas, put some HEET in there and fuel injector cleaner. It was not doing this when the car was used on a dialy basis! Perhaps the fuel filter is messed up even though its not that old cause of the old gas in there?? I change that after I inspect the coils for cracking.

[Juglenaut]

Appears to me like a dead fire check for spark replace coils as needed. Can also be ICM, and/or two to three plugged or sticky injectors. Always check fuel pressure as a troubleshooting.

[Dave]

here's a shot in the dark...

sound to me like the Catalytic converter is plugged up, or like there's some other obstruction in the exhaust system (or even in the intake ... check that air filter, it's quick and easy)

Here's why I think that ... If the cat. is slightly plugged, it'll allow enough exhaust flow at idle/part throtle, but once you start to accelerate more, there is too much exhaust for the exhaust system to get it all out, and then the exhaust backs up and stalls the engine.

--Dave.

[zegoldfish]

I second the vote on the cat. I was having this EXACT problem. After about a month of checking this and changing that, I just up and decided to gut the cat and viola! Problem solved.

[SappySE107]

It runs fine when its cold? 100% normal? Where are you located? Scanning the computer would be useful to see what its doing. Have you ever changed the O2 sensor or the coolant temp sensor? Id also suspect dirty injectors but if its only happening once its warmed up, its either a sensor still or your fuel pump. Mine would run great cold but once the engine warmed up, and the gas got hot, the pump started throwing a fit. I showed 40 PSI at the rail but when I pulled the lines I could see the flow was pretty bad. Of course, I didnt check the pressure with it idling and giving it some throttle either. Check that out as well.

[Juglenaut]

I would agree with sappy fuel pumps tend to fade in normal (summer) hot running temps when they start to fail. A o2 should be changed every 25k or less if they prove that they are faulty.

[Dave]

The crappy thing about Catalytic converters is that they can flow fairly well when cold, but as they heat up, the crap stuck in them can expand and block off the flow.

but it can be any one of the issues mentioned.

--Dave.