I have a 90 Lumina Coupe with an intermittant stalling problem. When it
stalls it is always warm, but otherwise there is no rhyme or reason. I can
be going 60 on the freeway, stopped at an intersection, or parked at a
store and just starting it up to head home. I no longer can go anywhere
without a bit of anxiety that I will get there on time or even at all! I
have taken it to my local mechanic who changed: PROM, Fuel Pump, crank
sensor, and he sent me to Chevy who changed: O2 sensor, temp sensor, crank
sensor, Ignition Control Module, Map Sensor, and now the "brain" whatever
that is! My main question is did the messed up brain make all those parts
go bad? or did the mechanic want to change something even when the scope
showed nothing wrong?
By the "brain" I'm just going to assume you're talking about the ECM.
If the car wasn't bringing up any codes the mechanic would be running blind as to what could be wrong, with modern day vehicles, there's so many things that can cause a vehicle to not run, and all of those could cause it. There's nothing else he could do other than replace the parts that will cause it to act up.
A faulty ECM won't make anything go bad, it will just make it so the vehicle will act up in one way or another, or will make it just not run. So in short, it didn't make anything go bad on your car, but can bring up symptoms that certain parts are going bad.
So is your car fixed now or not?
It could also be some bad wiring leading to the sensors, I doubt that all of the sensors went bad at once or that the ECM caused them to go either. Considering that the car is fifteen years old I would say wiring.