I was wondering about some of the components of the charging system in your car.

How old is your alternator?

Would the voltage regulator be the same age as the alternator?

How old is the battery?

What does your economy gage read when the car is about to die?

Have you measured what your charging system is putting out?

I had a stall once in traffic. It was at a stoplight. I was able to restart the car but, it would want to die idling in gear. The car would have a stumbling idle and the economy gage would be at half-way or worse into the red. For me it turned out to be the alternator. It was old and could not maintain a charge. I first tried the cheap to replace voltage regulator which is near the alternator. It improved but, did not keep the charge up high enough in gear. I replaced the alternator with the newly purchased voltage regulator and I had success.

Good luck with your diagnosis.

Mike McKinney

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1989 300CE - 269,000 km
1994 SL600 - 59,000 km