I was driving my 1992 940 when it started to roughly pulsate the RPM's between an almost dead idle to 1500 when idling at a Dunkin Donuts drive-thru. I took it to the dealer who found no codes, and also found it running fine. It drove wonderfully all night. It sat in the drive over night. When my wife started it the next morning, it stalled. She started it again and it reved to about 2000, then dropped back to less than 500, back up to 2000, down to a sputter, up to 2000 and to a stall.

What is strange is that it usually runs great and we cannot find a pattern to the times it starts this pattern. It did this when hot, and again when cold, and then runs for some unknown reason it runs fine.

Help. No one seems to know what to do. Has anyone else experienced this and does anyone have any solutions?

Try cleaning the throttle body and idle motor.

I should have mentioned that I already tried this. However, here is another development for the mystery our dealer cannot solve.

Last night I pulled the fuse on the engine computer and let it sit for fifteen minutes. I replaced the fuse and the engine started and ran fine. I took it for a drive to downtown and had no problem. I am now letting her sit to see if the problem will replicate itself. If so, I'll try the "fuse pull" again.

If this proves to reset the computer and keep her running, do you have any idea what such a pattern with the engine computer might indicate? Is there some sensor I should look at that is marginally malfunctioning? Is the computer needing some adjustment? Other ideas?

Thank you for your help.

If resetting the computer fixes it then it is an intermitant fault.