Hi all,

I bought my 1986 300E 2 years ago with 120k miles on it. Engine stalling has been a constant problem.

When I first got the car, it had poor acceleration. After a couple of months, the car would start cold. When it warmed up it would start to shake and stall. If the gas pedal was held, say half way, the engine would rev up and down from 4k to 500. This would happen for 5 10 mins then the engine would run normal.

Things I did which improved issue mentioned above were:
1) replaced fuel pump and filter.
2) replaced oxygen sensor
3) replaced spark plugs (**This improved the idle)
4) adjusted air fuel ratio (** This made a huge difference. Car had more power.)

After, a couple of months doing this, the engine would stall on idle after it warmed up. Replacing spark plugs kind of made this symptom go away. I was using NGK spark plugs from Autozone. Replaced spark plugs many times. Finally, got fed up and bought original spark plugs, one without resistor I think, from online.

The car ran good the whole winter until now. The car stalled in the middle of the highway last week. It was raining heavy. When I opened the hood, the ECU area was wet. There was water on top of connectors, fuel relay, OVP etc. The car would start but ran really rough and when given gas, it would not pick up. I could hear miss firing in the air filter area from time to time. Tried many things nothing worked. Finally, took the OVP relay out and immediately the car ran smoothly. So I drove home without the OVP relay. Acceleration was really poor and I think took more gas. I guess it removed power from ECU unit.

I know the OVP relay is good. I am assuming, its water getting in to some connection.

Has anybody have had this problem? Water getting in to connections, etc. Any suggestions, what to look for?

Thanks.