This problem has driven me nuts (and broke) for months. My 1992 745 stalls or runs rough at idle. Runs fine at speeds over 750 rpm. Gets good mileage and has lots of pep. The car uses the Rex/Regina engine management system. Had a new head gasket installed last Sept. Ran fine. Went through a deep puddle in October. Engine stalled out, restarted and dried out, then stalled and went dead four days later. Mechanics get it going but the idle has been rough and stalling problem resurfaces intermittently. No error codes, ever.
I have replaced:
Catalytic converter, Fuel pump; fuel pressure regulator; engine temperature sensor; oxygen sensor; fuel filter.
We have checked fuel rail pressure OK. Disconnected the cold start valve and re-flashed the computer module. Fuel injectors cleaned. Throttle body and switch assembly cleaned. Auxiliary ground run from battery negative to all ground points on chassis, firewall, intake manifold etc.
Idle air motor swapped for a known to be good.
Vacuum lines checked.
After replacing the O2 sensor the car ran fine for a month. Then started stalling again. The stalling seems to start after the engine has been running about 15 minutes. We replaced the new o2 censor with another one, but that did not correct the problem. We swapped fuel computer modules which didn't help either.
State emissions report came back showing the car was running rich.
I am not running rich. I am going broke trying to solve the problem.
What did we miss?