I have an 87 300e and have exactly the same problem as described,
however I've already changed the Overvoltage Protection Relay on my
car as part of an ongoing effort to sort out a series of problems with
the fuel injection system, so far including the OVP, the ECU, fuel
pressure regulator and all six injector nozzles.
The ECU was changed because it was corroding inside, the regulator to
cure a warm start problem and the injector nozzles because the new
pressure regulator caused them to start leaking :)
The problem is intermittent and seems to go away each time I change a
component, only to come back after a few days. The idle speed is
erratic and now it has started stalling in traffic. While running at
low speed it alternates between an apparent misfire and picking up
speed on a steady throttle.
I'm about to change the oxygen sensor to see if that works, as I've
seen a previous post identifying it as a possible cause of the
problem. My mechanic fiddled with it last week and cured the problem
temporarily so it's looking a likely culprit. If that doesn't work, it
will be the idle control valve next.
If anyone has successfully sorted out this issue, would love to hear
how to fix it before i have to blow a fat wad on the fuel distributor
because nothing else works. Love the car but this is driving me nuts.