I am a newbe and if this question has been answered my oppologies. After several trys with this search engine I found nothing at all.

I have a 1990 740 Regina (new to the car and not sure if it is GL or what) Does have power windows.

Question: Are ECU brains interchangable as long as they are the same manufacture? Mine are Siemans and the original Volvo number is 8601056 the Seimans number is S101590202E. I found one in a junk yard that is Volvo #6842882 the Siemans # S101590202A. I drove the car home from the junk yard using the junk yard ECU. It did fine on the highway but when I came to a stop it sputtered and cut off similar to what the original does, except it started back easier.

I will do one question at a time for my own confused self.
Thanks and look forward to owning or blowing up this Volvo depending on whether I solve it's problems.

BTW I have replaced the Idle Air control valve (with used one that works) also the Air Mass unit (tried 3 different used). New Fuel regulator? on top of the fuel rail. And New fuel filter.

 

Have you clean the throttle control body? They stick when dirty which causes the car to stall when it switches from driving to idle mode. The valve closes, sticks and doesn't open up fast enough to avoid the stall. Also check the MAF air duct to make sure it doesn't have a hole.

 

I have purchased some throttle body cleaner and plan on doing that asap, as well as a tune up. I put a new MAF air duct on the car not long after we bought it. It was the beginning of our problems. I spent close to $500 with the mechanic before I decided to take things into my own hands. Next I need a good aftermarket shop manual.