UPDATE !!! Problem appears to be solved.
...but will post this for other members.

I have a 1991 300e 4matic
170,000 miles approx
Detailed service records from prior owners.

Has original fuel pump, plug wires, distributor cap and rotor.
The OVP was replaced in '06, but no record of any sensors being replaced since new.

The car has been good to me since I bought it about 10 years ago.
It's one of many cars I have, so it's only seen 30k miles since I've had it, but it
is driven at least once a week.
It has never left me stranded and it's one solid car, much more so than my E55.
I love the feel of the 300e out on the open road.

I have the best benz tech in Denver, but I do like to tackle things myself and then if it's beyond my capabilities, I take it in and have the pro figure it out.
Besides, I never know what amazing cars I'll see in his shop, such as the '54 gullwing that I drool over every time I see it.


In the past week or so, I've had the following problem.
The 300e starts immediately and idles smooth as glass until it warms up and the thermostat opens.
Then the severe missing starts and it eventually dies.
Will not restart for a few hours and then the same thing happens again after it warms up.

Over the past two days it did this 5 times.
I checked the resistance readings on the crankshaft position sensor and coolant temp sensor.
Checked for a leaking EHA
Checked the grounds
Checked the OVP and MAS relays.
Checked fuel pressure
Checked for spark
Replaced the rotor, it was cracked.
Checked vacuum lines.
Cleaned idle air control valve.

...but still the problem remained.

Then I glanced on the workbench and saw an idle air control valve from my '90 Carrera 4 that I had left over when I removed the supercharger and went back to stock induction.

Aside from the connector, it appeared to be the same ICV (different part number though), so I soldered a couple jumper wires to install it.

I then tried the 300e one more time and sure enough it died after warming up and would not restart.

I immediately removed the benz ICV and installed the one from the Porsche.
It stumbled a bit, but started within a couple seconds and the idle smoothed out.
It's now been idling for over 90 minutes, smooth as glass.

I'll order a new one and hopefully this issue is solved !!!

Back to the drawing board... problem is back.

I did replace the original fuel pumps and filter...
At 180k miles, I'm sure I was on borrowed time anyway.