1990 Cadillac Deville Stalls and backfires

Lets get the fuel pressure check with a fuel pressure gauge designed for your fuel system-to rule out the fuel filter, pressure regulator and fuel pump-could be bad fuel- I need the fuel pressure readings for evaluation and direction to take-

Or you can do below immediately when is stalls out to determine if its fuel or spark problem

Get a carb cleaner and spray into the carb or the throttle body on an EFI. Did it start and die? If not disconnect a sparkplug wire or 2 and ground it to the engine -have helper crank engine over-do you have a snapping blue spark? If so-you have a fuel problem, check the fuel pressure to rule out the fuel pump/pressure regulator and listen to the injector/s are they pulsing or hook up a noid light.

Fuel pump/Pressure Regulator and Injector/s checks out-start checking the ignition system-power to coil, coil/s itself, distributor pick-up, control module, Cam and Crankshaft sensors.

If both fuel and spark is present-check the valve and ignition timing, this will lead you to problems with compression and valves opening and closing at the wrong time

TYVM for using 2carpros and I'll be waiting for your return as needed-

Razzy codes need to be checked first, off and warmer on the heater controls with the key in the on position. Look in the fuel message center for the codes, starts out 8.8.8 and ends with 0.7.0

I believe for the backfire the AIR pump and Diverter valve are bad