1996 Gran Sport 3.8L starts and dies when engine is warm.

[R Holland]

Okay the engine starts fine when cold. The engine starts fine when up to temp and restarting within 5 minutes of shutting it off. If the car sits for 15 minutes to 45 minutes, the engine will fire and then drop down in rpms almost stalling or it will just stall. If I give it a bit of gas when the engine fires and keep the rpms up for 30 seconds the engine will stay running. The car has had a complete tune up, new fuel pump, gas tank, fuel filter and fuel pressure regulator. Fuel pressure is good and steady. The intake gaskets and plenium have been replaced. TPS , MAP, MAF, Crank and Cam sensors have all been replaced. All vacuum lines have been replaced. No codes are being thrown. Anyone have any ideas?

[R Holland]

Okay, well I see no one had any insight to this issue. After searching the internet, I found a few things that may be causing this issue; crank sensor and MAF seem to be the big two mentioned. The MAF sensor I had on the car was aftermarket. I purchased a new AC Delco unit from Rockauto and installed. Engine runs better and no more stalling problems.

[Schurkey]

Thanks for the update.  Someone else will probably benefit from your discovery of the defective aftermarket MAF sensor.

[Padgett]

In a '96, an OBD-II scan tool should be able to monitor the MAF, IAC, and TPS readings.

Edited March 24, 2016 by Padgett

[rich_e777]

PCV valve?

[Imp558]

This thread lay dormant for nearly a year and it was that simple? The description was indicative of a MAF too. I never saw this one, we're really not that ignorant intentionally.

[oldparts]

I too have a similar problem, just bout the 1st gen 92 cutlass supreme conv. It has a plugged cat, failed emissions...researched about why cats clogged and they mentioned a lean condition....so I started replacing 02 sensor, cooling temp sensor, MAP, EVAP. cleaning EPR valve and channel, cleaned throttle body, replaced battery and ignition switch key lock cylinder.....started up fine and was purging air from coolant system and noticed as I revved the engine to 2500 it would die, I tried it several times....reving the engine slowly then about 2500 or 3000 rpm it would die, Is this because the plugged Cat? Do I need to go through relean idle procedures or can I reset by pulling ECM fuse for 30 seconds and replug while the key is in the on position?

[Psych0matt]

I too have a similar problem, just bout the 1st gen 92 cutlass supreme conv. It has a plugged cat, failed emissions...researched about why cats clogged and they mentioned a lean condition....so I started replacing 02 sensor, cooling temp sensor, MAP, EVAP. cleaning EPR valve and channel, cleaned throttle body, replaced battery and ignition switch key lock cylinder.....started up fine and was purging air from coolant system and noticed as I revved the engine to 2500 it would die, I tried it several times....reving the engine slowly then about 2500 or 3000 rpm it would die, Is this because the plugged Cat? Do I need to go through relean idle procedures or can I reset by pulling ECM fuse for 30 seconds and replug while the key is in the on position?

hey, new Sam, you're bumping years old threads

[Imp558]

If the converter is plugged that would be something to address before you do more testing.

[oldparts]

oh yeah....I do have to do that first....silly me

[movielover40]

My Pontiac Grand Prix did same thing.

 

It would run great then just stop. Start right back up and run great.

 

Turned out to be MAF...

[oldparts]

I don't have a MAF, but I just got a NEW carb compliant catalytic converter on ebay for 50.00. I need to do that first...I 'll post the results...has any one done a "pull ECM fuse" to reset ...this could be one of the problems and it is getting worse now because it erased the memory of a plugged cat, and it kept adjusting to a lean condition....then after putting the new battery in it reset to factory, but with a lot of back pressure with a plugged cat....it cuts out at 2500 to 3000 rpm....today I started it up and couldn't give it any gas before it stumbled and quit, a lot worse than yesterday.....anybody experience that?

[Nas Escobar]

I too have a similar problem, just bout the 1st gen 92 cutlass supreme conv. It has a plugged cat, failed emissions...researched about why cats clogged and they mentioned a lean condition....so I started replacing 02 sensor, cooling temp sensor, MAP, EVAP. cleaning EPR valve and channel, cleaned throttle body, replaced battery and ignition switch key lock cylinder.....started up fine and was purging air from coolant system and noticed as I revved the engine to 2500 it would die, I tried it several times....reving the engine slowly then about 2500 or 3000 rpm it would die, Is this because the plugged Cat? Do I need to go through relean idle procedures or can I reset by pulling ECM fuse for 30 seconds and replug while the key is in the on position?

 

If you suspect a plugged cat, cut the cat off and put a normal pipe to connect to the rest of the tubing. If the car runs better without a cat, then your cat was clogged and you need to replace it. You can't throw parts at  a car and expect it to run better.  The biggest tell sign of a clogged cat is a sluggish engine and the engine cutting off, but it shouldn't even rev up that high. 

 

My experience with the 60 degree V6 engine is that if an engine cuts off at 2500 RPM or higher, it's the fuel injectors. The way you usually see this symptom is that the car will idle fine when parked but if the engine is under load it will cut off instead of receiving more fuel from the injectors. Very common issue on the MPFI V6. 

 

Also, AFAIK, relearn idle is moreso an OBD2 thing. OBD1 could control idle but whatever figures were stored would disappear when the engine was turned off. This is why usually on an OBD2 car, the SES light will stay on even if you fix the issue whereas on an OBD1, the light is triggered after running but won't stay on. 

 

I don't have a MAF, but I just got a NEW carb compliant catalytic converter on ebay for 50.00. I need to do that first...I 'll post the results...has any one done a "pull ECM fuse" to reset ...this could be one of the problems and it is getting worse now because it erased the memory of a plugged cat, and it kept adjusting to a lean condition....then after putting the new battery in it reset to factory, but with a lot of back pressure with a plugged cat....it cuts out at 2500 to 3000 rpm....today I started it up and couldn't give it any gas before it stumbled and quit, a lot worse than yesterday.....anybody experience that?

 

You should have started a new thread. Someone thought you had a MAF because they assumed the 3.8 was the engine you had. The Cutlass didn't have any variation of the 3800. All of them were "Chevy" V6's. 92 would have had the 3.1 MPFI or the 3.4 DOHC engine. MAF wasn't added until 1994. 

 

Also, since your car is a 1992, you don't have a post cat sensor. You're only running one sensor, and it's on the exhaust manifold pipe before the catalytic converter. The computer itself doesn't know the reading for the exhaust after the cat, only before it. 

 

The stumble and quit is a tell sign that you're exhaust is clogged... in other words your cat, since it's the only thing that can clog. A muffler can too, but doesn't happen often unless someone stuffed something in it. Usually mufflers rust out. I mentioned this at the beginning, but if you have a way to, cut the catalytic converter off and it should run normal after that. You won't have a SES light since there's no post cat o2 sensor. IF you have the same issues, then it would be time to look at the fuel injectors.