I'm having a similar, but intermittent, problem on my daughter's '87 300E.

In troubleshooting, replacing (O2 was due at 282,000 mi. and filter) and checking various things, I decided to unplug the EHA and see what happened. The problem has yet to happen, so that eliminates a number of possible items, including fuel supply and ignition. I have to find time to get back to it, but now I can isolate the problem to anything related to the electrical fuel injection control.

Good luck! Any anyone who finds a solution, please post results!