Will not start/run after it warms up

Part of what you described is often caused by a collapsed pick-up screen inside the gas tank. The clue is the engine runs best at highway speed, and tends to stall when the highest volume of fuel is being pumped, which is during coasting. Sufficient volume cannot get through the screen, so pressure drops. You can identify this by attaching the fuel pressure gauge where you can see it while driving, and watch what happens to pressure when the problem occurs. If the pressure drops, you may be able to overcome the problem by disconnecting the vacuum hose from the fuel pressure regulator and plugging it. That will cause pressure to increase and reduce the volume of fuel the pump needs to pass.

The idle air control valve is not a sensor, and it cannot allow any air to leak in. Chrysler is the only manufacturer that never needed a mass air flow sensor to make their engines run right. All other manufacturers use that sensor on all or most of their engines. If there is a leak in the fresh air tube between the sensor and the throttle body, or a vacuum leak anywhere else, that air will not go through the sensor and will not be measured. No fuel will be calculated to go with that air. Those leaks can cause a stumble, hesitation, stalling, all the way to a crank/no-start. A clue is the engine will fire when starting fluid is sprayed in at the air filter, proving you have spark.

When you have a mass air flow sensor, the MAP sensor is used to measure barometric pressure, and as a back-up strategy when a problem with the mass air flow sensor is detected.

You should be checking for loss of spark too. Most commonly you will also have no injector pulses and the fuel pump will not resume running during cranking. Typically that is caused by a failure of the crankshaft position sensor or the camshaft position sensor.

For the fault codes you listed, your best approach is to watch their readings on a scanner during a test-drive. For two contradicting codes, start by looking for a rubbed-through wire that got cut where it lays over the sharp edge of a metal bracket, and corrosion between mating and adjacent terminals in electrical connectors.

One more thing to consider is the fuel pump only runs for one second when you turn on the ignition switch. It resumes running when the engine Computer sees signal pulses from the crank and cam sensors, meaning the engine is rotating, (cranking or running). On older GM products, the fuel pump resumed running from a tap on the oil pressure sending unit. If you lose oil pressure, the fuel pump turns off. That is a safety system in case a fuel line gets ruptured in a crash, to prevent pumping raw fuel onto the ground where it would become a fire hazard. It was fairly common for stalling to occur from the fuel pump turning off due to low oil pressure or a defective sending unit. Oil level that is just one or two quarts low can cause this long before the pressure gets low enough to trigger the "oil" warning light.

Good morning.

When you checked the fuel pressure, did you check it when the car shut off to verify you are not losing pressure causing it to stall? This would make sense as the other codes are related to lean and rich conditions.

Roy

I was just thinking. The ignition modules were a issue with these. You can remove it and have it tested at a parts store. That is a free service as well.

Roy

Your engine does have a mass air flow sensor, and if it fails, you'll still have spark. Try banging on it, then cranking the engine. If that works, the sensor has bad solder connections inside. More commonly, when the engine is idling, banging lightly on the mass air flow sensor will cause the engine to stall.

When the mass air flow sensor fails, the MAP sensor is supposed to become the back-up strategy to allow the engine to run poorly, but run. GM had a huge failure rate in the late '80s with their MAP sensors, so they sold them to Chrysler. With a failed MAP sensor on a Chrysler product that got towed in, we often surprised owners by driving the vehicles into the shop under their own power. The secret was the engine would continue to run as long as the accelerator pedal was moving. Direction and rate of change didn't matter; it just had to be moving. I don't know if that works on GM engines. MAP sensors of that original design are all long gone. The redesigned sensors are pretty reliable.

Hi Asemaster6371.

You're right. One of my sources shows the MAF sensor for your engine available from four sources. Another source doesn't show that sensor. Sorry about that.

This makes the MAP sensor your main fuel metering contributor. One thing to be aware of is the normal range of signal voltage is 0.5 to 4.5 volts. Anything outside that range is what triggers a diagnostic fault code. If the sensor develops the wrong voltage, it will not set a fault code as long as that voltage stays within the acceptable range. A tenth of a volt off will cause a big performance problem. Besides a failing sensor, keep an eye out for a dry-rotted vacuum hose, condensed fuel vapors blocking the hose, and vacuum leaks.

Okay.

Did you check the fuel pressure as I suggested back a bit when it shuts off?

Did you also inspect the connector to the ICM? That was a know issue back in the day.

HI CJ, hope all is well with you.

Okay, the pressure is too low. Should be 45 lbs constant. 38 is not good enough.
You will need to replace the pump.

Roy

Your welcome. We are hear to help

I would try the temperature sensor and if that doesn't do it a new PCM. Let me know if that fixes it.

Did you verify the fuel pressure? You need to be sure you have 45 pounds of pressure.

Did you check for spark or take the module and have it tested?

Roy