I have a 1990 780 Turbo, 160,000 miles. I have been chasing a problem for months, and am starting to think I am chasing my tail. The problem is intermittant/sporadic. When the failure happens, it is usually after driving from a cold start for about 3-5 minutes, the engine shuts down, as if someone turned the ignition off. After sitting for 3-5 minutes, the engine will start , and until recently would continue to run throughout the rest of the day. More recently, the failure may happen 4-5 times before I can get the engine to run until I shut the engine down and re-start at another time. The OBD readout indicates that the engine speed sensor is intermittant or failed. I have replaced the coil, the engine rpm sensor, I have rebuilt all of the connections on the positive side of the battery cable (some looked flaky), I have replaced the ignition switch. During the most recent failure, the air conditioning green light was flashing when the engine shut down. The air conditioner was not in use at the time. I haven't determined a direct correlation yet, but it seems to die more frequently when the outside temperature is warmer.

Does anybody have a clue what might be going on and how to remedy?

Thanks, Larry T