Car stalls when slowing down or stopping,when on the highway it sputters

lumpleby

I've replaced fuel pump,02 sensor fuel pressure regulator,fuel filter . Before replacing all that it jerked on highway going 70 I slowed down and it went fine for 5 more miles then it died going 60, I pulled over and tried to restart and it wouldn't I put 2 bottles of heet into gas thinking it was water in my tank or bad gas, it started up and ran fine for a little bit had fuel pump checked and it only put out 30 pounds of pressure so replaced all above and it still sputters and randomly dies, but starts up again. No check engine light has ever came on to produce a code

lumpleby

Had iginition module checked it's good, sprayed carb cleaner every where it was fine. When we got back into garage I turned air on high and car died

imidazol97

What Pontiac is this? Which engine? Which year?

lumpleby

1994 poniac grand prix 3.1

imidazol97

I was hoping it was a 3800 engine. I am familiar with those. How many miles?

I would suspect the crankshaft position sensor. Watching the tachometer should show that it's not getting any timing to the engine and no spark when it acts up. When engine dies quickly, the tach is dead as soon as it happens even though engine still is rotating.

Bad wire to the crankshaft position sensor can also give trouble.

There is a troubleshooting method for the ISC module under the coils.

Somewhere I had heard that symptom about turning on the high fan speed with its high load killing the engine.

You might check the grounds if there is more than one from the battery to the fender and to the engine. Make sure there's a clean contact at the ground end--loosen and retighted, e.g..
Check for any grounds from the engine to the body, firewall, etc.. Be sure they're clean and intact.

lumpleby

278k on it. I'll look into that

lumpleby

Wouldn't the crank shaft position sensor trip a check engine light? 

imidazol97

No check engine light from CPS or the cam sensor, assuming it has one. I'm familiar with 3800 engine. Watch the tach to see if engine quits getting impulse from cps. Of its fuel or other tach keeps trying. Firing, while engine odds turning.  Cps usually have trouble when really hot in the area after driving because the magnetic fields are weakened. If engine doesn't restart after stall till itcools half an hour, try pouring cold wter on It right next to balancer. 

Spark control modules interchange among lots of gm cars. Try a used one from friends car or from pick and pull.