1990 Pontiac runs rough then quickly dies

[soxnut22]

I have a 1990 Pontiac Grand Prix with about 130000 miles on it. It had been running fine until one day when it stalled and died. I could not restart it so i towed it back to my garage. I thought there might be ice in it, so i tried to fix that and it didn't work. I replaced a PCV valve hose that was cringed. After doing that the car eventually started but just barely. When it runs it will idle extremely rough for about thirty seconds and then die. Next, i took off the fuel line at the engine and turned the key on to see if the gas was coming through and the gas came through fine. I also noticed that if i spray starting fluid directly in the carberator the car will run fine. This leads me to believe that there is a fuel problem, but the car is getting gas to the engine. I replaced the MAP sensor and that did not solve anything. I also tested the fuel pressure regulator and the pressure was fine. What else could be wrong? If you have any suggestions at all please reply.

[SUERED]

Sounds like Fuel Filter to me. Have you considered this?

JR

[soxnut22]

JR one of the first things i did was test the fuel filter but it seemed fine. Also if the fuel filter wasn't working then i dont think the gas would be able to come up to the engine as good as it did. Any other suggestions??

[jlward60]

My 1990 pontiac had the same problem. I checked everything. Then one day I was checking things out on the internet and found a GM service bulletin for 1990 grand prixs with faulty PROM's in the ECM that malfunction and cause the air/fuel mixture to go wacky. I changed the one in mine and it runs like new. Hope this helps.

[jlward60]

Also, you can find a copy of that problem and the Bulletin at www.misterfixit.com/336506.htm

[soxnut22]

I have not checked the Ecm of the PROM and that very well might be it. I was just wondering though if your car had the same problem as i explained or the same problem on the message board you found. My car died going about 20 miles per hour and would not restart. It would want to start and it would run for about a second or two and then die. Eventually i got it to start, but i think it was because i forced it. When it does run if u tap the accelerator it will die. It will not move, and the engine only runs for a short amount of time at an unstable idle and then dies. Is this the same problem you had?

[SUERED]

Hi,

Wisdoms flow from experience but actually many things could be the problem here. If a fuel filter becomes 90% clogged (or whatever that percentage could be), then it will feign good health. You would be OK at idle and maybe even low trottle. The first time you gun the engine-floor the pedal, the fuel cannot flow fast enough through the failing filter= stall. ...Something like clogged arteries and chest pain I suspect!!
Wish I had other ideas, but others can help.

JR

[jlward60]

My car died to and would not start. I had to keep the throttle to it to keep it running. The moment I would let up on the throttle it would die no matter what speed you were doing. RPM's had to be kept above 1000 for it to run.

[doccourage]

I had something similar.As it turned out
it was the Fuel Pump Resistor.It was a recall
for a short time.

[jon95se]

could be the regulator, could be the injectors, could be crank sensor, could be idle air controller, could be TPS, so many things. on and on and on. could even be a clogged catalytic converter.

[SUERED]

Sounds like time to employ a code reader device.

This remedy saved hassles for my sister in laws GP:

[avsphere]

Hey,

I'm going throught the same problems your dealing with. My car stumbled out of no where on my lunch heading back to work. I was going around 25 mph when it just died out. Checked the fuel pump and I had good enough volume and the filter was good, fuel pressure is good but it does start if i spray carb cleaner in the throttle and then runs for a bit and then dies when it gets hot. The only thing I did see is that the fuel injectors have a weak pulse via noid light. No codes found either.I've got fuel and spark and once I got the car running it runs roughly like its not getting the proper signal for fuel.. so I'm going to replace the ignition module, so I'll see what happens.

[nova_gh]

same problem with my 91, Prom has a tendancy to loose programming, the ecm needs a constant power source to stay programmed, disconnecting the battery, even for a split second, will reset it. Then the car will do exactly as you've described. I would get it to the GM dealership and they'd reprogram it, and it would run perfectly!

[WickedClown202]

Do they charge you to re-program it ?

[Stan King]

I fixed this identical problem on my '90 Pontiac...Cause: Intermintent open Oil Pressure Switch.....Detail: When the ignition Sw. is turned-on, the fuel pump relay turns on for 2 seconds and pressureizes the fuel system. After 2 sec. the relay opens and the oil pressure energizes the parallel connected oil pressure sw. and turns on the fuel pump.If the fuel pump side of the oil pressure never turns on this sw. the fuel pump will not continue to run and the motor stalls....REMEMBER THE OIL PRESSUE SW. HAS TWO SWITCHES INSIDE, ONE FOR OIL PRESSURE AND ONE FOR FUEL PUMP PWR...THIS IS A SAFETY FEATURE TO PREVENT ENGINE DAMAGE IN THE EVENT OF NO OR LOW OIL PRESSURE...