Greetings,
Someone in this forum had said "Welcome to Mercedes, fix one thing, another breaks", boy he was right........

As you all know I had huge problems with my idle control system and finally the idle control unit fixed all of them, then the car started to overheat so I am pulling the radiator and taking getting it fixed.

Now I took the car to the mecahnic to do the fuel/air ratio adjustment as I messed with it while I was diagnosing the idle problem and he said the ratio was stuck at 50%.... Meaning that o2 sensor or Engine Control Module or Frequency valve wasn't working. And told me to check it...... My stupid $120 manual gives no information about how to check any of those things, but it does tell you what they do and where they are at (except I can't figure out where the engine control unit is at).

please help again