I have a 1991 buick regal stalls and shut off after warming up

test the fuel pressure sounds like fuel pump getting hot and shutting down

The automatic idle control valve may have stopped working or the control module that operates it.

When the engine warms up the engine computer goes into closed loop mode and relies primarily on the O2 sensors and the MAF sensor to calculate the correct fuel to air mixture - if one of the O2 sensors is fouled or the MAF sensor is not working properly, this can cause the problem.
Given the age of the car, I would also check the idle air control (IAC) and channels, the EGR valve and the throttle body for carbon buildup.

Hi,
You need to get your engine coolant thermistor checked and tested. This is what tells the ECM when the engine temperature is at normal working temperature and turns the idle down.
But when the idle won't come down from cold to warm this is usually the main fault.
Hope this helps.
Thanks
Jason

When my 94 Regal GS frequently wouldn't start for 30 minutes to an hour after being driven, it was the crankshaft positioning sensor that needed to be replaced. I also replaced the harmonic balance pulley. The car ran more smoothly and started everytime.

sounds like it's tied into the coolant system..

Sounds like your car is overheating. If you have a temp gauge it should show that. If you just have an idiot light, by the time it comes on it's already too hot to operate. AFTER the car is cooled down, open the radiator cap to see how much coolant has been lost. Chances are there is alot missing. Add WATER (no sense in adding coolant if it's going to leak out) and idle the car at home. Look underneath as it warms up to find where the leak is.

Sounds like the EGR valve is bad.

I have found the most common part failure issue with the ignition system is the crank sensor, also called by some the TDC sensor.

check ur to see if ur catalytic converter is clogged