I haven't read the thread, only the title, but if you can get the engine started. Let it run while you go under the hood and try to systematically wiggle some of the wires....in particularly to the CPS and ignition/EZL system. I missed like 2 weeks of work trying to figure this same issue out on my w201. Car would run and then die randomly once put in gear. Sometimes I could drive it for miles, then it would shut off. Finally did what I'm telling you to do and found one electrical female connector was detached from the wire on the EZL system, but I didn't see it because it was covered by a black outer sheath and terminated into a single pin coupling that was connected to the other end of the plug. It was the thing circled in yellow. This is of course on the m103, but it may apply to you as well.

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1990 190E 3.0L