I had a similar problem (mine also had hot start problems) with my 89 240 sedan. Ended up replacing FP relay, fuses, sensors and various other items tested with another ECU never fixed the problem.

I was under the hood while it was running and I inadvertantly bumped one of the 3 wires that connect to the positive battery lead (small one that goes into the harness on the shock tower), the car died and wouldn't start. But would turn over and all accessories would work.

Wiggle wire, car starts. I cut the battery leads and reinstalled them with a new clamp.

I haven't had a stalling or starting problem since (4 months 5K miles)knock on wood.