94 E320 Surging idle & abnormal starting
 

The car has had a starting problem for awhile, below 50 degrees, car starts fine. Above 50 degrees or hot engine, the gas pedal needs to be depressed otherwise it just cranks but won't catch. Now a surging idle has developed where the idle goes up and down and after 10 or so cycles of this the engine stalls. I also noticed that there is a lot of black smoke coming out of the tail pipe. I checked for engine codes and a 10 is set meaning that the voltage to the mass air flow sensor is too high or low. any ideas? this car has been one hell of a money pit! $4000 in repairs in the last year (head gasket, transmission repair for no reverse, wiring harness, throttle actuator, water pump. radiator. I really don't expect this much repair expense on a well maintained 100K mile car.

With the list of items you say you've already replaced, I would suggest that your mass air meter might be bad.

What about the OVP relay?

Well it's in the shop! I will post results and $$$$ in a couple of days.

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sounds like the same symtptoms of my 95 c200.

surging idle when hot....
missing when cold...

I replaced OVP, throttle actuator, coolant temp, air temp and wiring harness.

Still does it, its at the dealers now. Theyve stated that there are voltage drops at the ECU - not sure what would do this.

Along with MAS air above upper limit (this has been swapped from another car and no go!)

Replaced the throttle actuator (cut into cable and insulation was mostly missing) and mass airflow meter. Everything appears to be fine...... for now......$2200

Well......as sad is it seems, you have now gotten over the hurdle of fixing the weak points of this car: head gasket, throttle actuator, and mass air meter.

It should be smooth sailing from here on out (knock on wood)..... :D