I have a newly acquired 1992 300E, 77,000 miles. I am not very knowledgeable about the 300E, or gas engines in general. I had driven MB diesels for 35 years. So I was startled and confused by a stalling problem I have had with this car.
Four times in the past 2 weeks, it has stalled shortly after starting. In 3 of the 4 cases, the weather had been damp (fog or rain) for some time. In the 4th case, there had been rain the night before, but a clear cold (30s) dry afternoon. In all 4 cases, the behavior was: Successful start from cold, drive a short distance (hundreds of yards in 2 cases, about 0.7 mile in two instances), then slow in preparation to stop. Engine dies. Difficult to restart. Have to put accelerator to floor to start it. Then it runs normally, and there is no further trouble once car is warmed up.
I have also had 2 incidents of difficult initial cold starts after engine sat for hours.
By the way, I am in Massachusetts, and daytime temps have been mainly in 30s and night temps mainly in 20s or teens. We have had frequent snow storms this month, as well as the rain and fog I mentioned.
Spoke to my mechanic. His immediate reaction was to start by replacing the OVP relay. From reading many posts here and on MBCA web site, I saw that OVP relay was regarded as a frequent culprit for many types of problems, including some more or less similar to my cold start/stalling, so I agreed to do it. The old one was of a different type that mechanic said was "out of date" and should be replaced on principle, anyway. I bought one from MB dealer, he put it in. While doing so, he observed that the spark plug wires were in mediocre shape and suggested we should do a tuneup, check plugs and wires, etc. But he said, let's do that after you drive a couple of days with the new OVP relay.
The 4th stalling incident occurred the afternoon after he replaced the relay, so clearly that was not the cause, or not the only cause, of the problem.
In thinking about the stalling incidents, I have noticed one other thing: The engine does not behave consistently when started from cold. Sometimes it goes into the high rev/delayed upshift mode, very noticeably, and other times it does NOT seem to do so. On at least two of the stalling incidents, when I have had trouble re-starting the engine and have floored the accelerator to start it, it has definitely gone into the high rev/delayed upshift mode. I suspect the engine weas NOT in that mode when it started the first time and then stalled. So it seems as if the engine either does not reliably "know" when to go into that mode, OR it cannot or does not do so when it should.
Any thoughts on whether there is one problem here, or two? Is it likely that the inconsistent cold start behavior (i.e., whether or not it goes into delayed upshift mode) is related to the stalling? Any suggestions for what would cause the inconsistent behavior?
Thanks for input!

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DavidB29
1992 300E with ASR
35 years of Diesels until now!