1997 Pontiac Bonneville SE 186,000 miles
Okay guys, here is the problem I am having with my car. When the engine is cold it will start up just fine and will run just fine for as long as I am driving it. The issue begins once the car is warmed up (200* F+ according to gauge) and then shut off for a period of about 30 minutes. After 30 min. I get in car and start it up, it starts just fine but will then misfire, stumble, and then stall unless I keep the rpm'* higher (2k-3k) for a few minutes. However if I do not prevent it from stalling, the car cannot be restarted until it cools back down. This usually takes about 1-2 hours. After I started having this problem with the car I began searching this forum.

These are the codes that were pulled, keep in mind these are from a period of several months.

P0171 system too lean (bank 1)
P0102 mass or volume air flow circuit low input
P0122 throttle/pedal position sensor A circuit low input
P0300 random misfire detected
P1655 evap purge solenoid control circuit
P0113 intake air temperature sensor 1 circuit high input

-Checked for spark, have it
-Replaced fuel filter
-Had parts store test ICM, failed, so I replaced it, didn't fix the stalling problem
-Replaced ignition coils
-Checked resistance of spark plug wires, all good
-Checked resistance of fuel injectors, all good
-Checked for voltage at fuel injectors, all good
-Replaced idle air control valve
-Checked MAF for damage, thin wire is in place and looks good
-Cleaned MAF with MAF cleaner
-Checked EGR valve solenoid with 9v batt., can hear solenoid pull in
-Checked for vacuum leaks, found a cracked fitting, replaced it
-Checked O2 sensor by applying heat then check resistance, good
After having done all these things without fixing the problem I knew I needed to check fuel pressure.

With the ignition on but the car off I only got 20 psi.
Started the car and pressure went up to 30 psi.
Rev the engine and pressure does not go above 30 psi.

Could a bad fuel pressure regulator cause the low pressure or is this solely a fuel pump issue?

Would low fuel pressure cause the warm restart misfiring, stumbling, stalling problem?

Anyone have experience with a situation such as this? Any thoughts, ideas, comments? Cause I am running out of ideas and really want to fix this problem.

low fuel pressure can cause issues because the fuel isnt what the pcm thinks it is. try sniffing the vacuum tube to the fpr, if it smells like gas replace it. while your there check for cracks in that line and the evap purge line to that boot, and inspect the boot alot of people have had vacuum leaks because it gets dry rotted. since youve replaced the filter the pump or fpr could cause low pressure try to cap the return somewhere and if it goes up the pump is not the problem

All those P codes you listed, are all low voltage related. And all those sensors/PCM share a common ground on the backside of the engine block near the oil pressure sensor. Inspect that ground grommet thats bolted to the backside of the engine.

Okay so as mike suggested I inspected the ground on the backside of the engine. With the ground terminal still bolted to the block I checked for continuity to another ground and it had continuity. I also pulled out both the ground buss terminals(driver and passenger inside on floor) and inspected them for corrosion. Both looked in very good shape but I still took a fine scotchbrite pad and cleaned them up a bit. I also pulled off the grounding point next to the battery and the one by the horn. Cleaned them up, reinstalled and still have the issue. Any other ideas?

you do the fpr and vacuum line checks i suggested?

jwfirebird - Yes I checked vacuum lines visually and also with some carb cleaner sprayed around fittings and hoses. Pulled off the elbow fitting and hose at the FPR and took a whiff. It did smell faintly like gas but it could just be from when I checked the fuel pressure, when I unscrewed the gauge from the schraeder valve some fuel sprayed out and could have gotten on the fitting, making it smell like gas. I did see a video on youtube of a guy who checked for a leaky FPR diaphram by pulling the hose off and running the vehicle for a bit to see if any gas comes out of the vacuum port on the FPR. So I did this and ran the vehicle for about 10 minutes but never seen any fuel come out, nor could I smell any after running my finger over it.

How old is the battery? With the low voltages at those sensors and low fuel pressure, I'm wondering if the battery is either going bad or if you have a bad connections at the battery.

My '97 SE was doing the same thing and after throwing a lot of parts at it(various sensors) I checked the fuel pressure and was getting about 25-30psi.Your fuel pump is on its way out!! As soon as I dropped the tank and replaced the pump my problems were solved!

If you doing your fuel pump you may as well change your lines too.Here'* a link to what I replaced on mine. More Information for SPECTRA PREMIUM SP07P1H

mike1995- I am not exactly sure how old the battery is, but my best guess would be at least three years old. About a year ago I was having a no crank condition so I pulled off the terminals and cleaned them up and tightened them up real good. But I will definately do that again and next time I can get it to stall I will check the voltage on the battery.

madcoachman- After I tested the fuel pressure and only got 30 psi while running I pretty much assumed I would be changing the fuel pump. And like you I also looked into replacing the whole unit. After all it was only $80 more than just the fuel pump by itself. I wanted to try checking out everything else that could possibly have caused the problem before I change the pump. The only other thing I can think of changing is the crankshaft position sensor, but from what I have read the sypmtoms are a bit different. So as you said I think I will replace the fuel pump, although I will have to wait for the weekend to do it. I will definately let everyone know what I find.

Thanks everyone for the quick responses and all the help!