'87 BMW 535i engine dies

I recently was given a 1987 BMW 535i, the previous owner replaced the two sensors on the vehicle and repaired a vacuum leak (those are the only repairs i know of) *NOTE* the previous owner did this to get the car running

The problem with the car is that it dies at random, some days you'll get in the car and start it and drive fine without a problem, other days it takes 2 or 3 tries to get the engine to fire then it stalls after the revs drop to around 800 rpms.

I've was told that the problem might be the engine computer that I can see is located directly in the glove compartment, what also led me to believe this is that I've started it up before and got out of the car to check something, upon sitting back down the car dies, same situation if I close the door.

I've noticed that if the car "plans" on running that day then the car revs to about 1200-1500 rpms at it's idle, then drops to around 800 rpms after it's initial warm up, however if the car "plans" on giving me trouble then it starts up at about 800 and stays there, there is no noticeable warm up of any kind


does anyone have any suggestions before i purchase a new engine computer for around $230?

I will be grateful for any assistance.