I have a problem with W124 -94, engine 2.0 or 2.2 litre with PMS engine management.

Does not start below zero but will start if pour fuel directly to throttle flap housing. Idle control motor does not seem to operate at all at any temperature.

Below is an email to a company that repair ECUs and response from them.

Any ideas how to proceed, experiances with PMS system et.c. ?



Question:

I have a problem with a car with PMS, please see ECU info below. Idle control does not work and engine sometimes stalls when accelerating and does not start when cold temperature.
I have tried to check some things like idle microswitch, pressure hoses et.c. and so far everything seems all right. Do you think this kind of failures is likely due to ECU or something else ?

Do you have ECU wiring schematics so that I could also check wiring harness et.c. ?

How much would you estimate for repair of this ECU ?


MERCEDES BENZ
015 545 70 32

SW 34.93
PM0009 4Zyl. [07]
SIEMENS 5WK9 110

Reply:

We have seen this kind of problem with the Siemens PMS before. It is not repairable due to the way the ECU is constructed.
You can probably get around most of the problems by adjusting the Throttle stop until it will Idle cold, it will then be a bit high hot but you maybe able to live with that.
Its worth checking that the Idle Motor is actually working by putting a variable votage across the motor connections to check operation in each direction. Dont put a straight 12volts on the motor but turn the voltage up until the motor moves.