Engine stalling at speed
 

Last year my 87 911 started intermittently stalling/dying while at speed, usually between 2000-3000 RPM while coasting (~50MPH) or decelerating but nowhere near idle engine speed. It doesn't do it very often, and can go hours/days of driving just fine. When it dies, the throttle just cuts out, the battery light comes on and the engine dies. It doesn't misfire or stumble or make any weird noises, the engine just shuts off. The electronics (radio, etc.) seem to continue working fine when this happens.

The other week I drove a half hour, parked, got back hours later and started it up, it was idling for about a minute, and then it died. I tried starting it again and it just cranked and cranked. I gave up, waited a minute or two and then it started up, I drove half a mile and then it died when coming to a stop sign. Then it would just crank again until I waited a minute and it started right up and drove home fine.

A shop looked at it a couple months ago and eventually reproduced it and replaced the DME relay and then couldn't reproduce it again, but they only had it for a day or two after that. It's died a few more times since then.

Any ideas on what to look at next or how to troubleshoot this?

First check out the coil. If it is the OEM original black coil, and has black goo seeping out, that is it. If no goo, leave it alone. There are no quality replacement coils. You can get a new coil from Porsche or Pelican and it is the silver Bosch unit that is a 50-50 chance it works from the box. They are junk.

Next up, replace the head temp sensor and the flywheel sensors. Get the BMW flywheel sensors. They are the same as the Porsche sensors except the wires a just a little longer, and way cheaper.

If the sensors have never been replaced do it as a proactive thing. And a new head temp sensor while yer in there!

There are several threads on this site that go through every step of trouble shooting. The flywheel sensors were my biggest issue for weird running.