94 E320 Surging idle & abnormal starting

[Jerry_Mullen]

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.