I have a 93 300e 3.2 HFM here with the idle fluctuating like it has an air leak. I can not find one. I have retrieved the following faults:
012 -Engine idle speed contact, air mass too large
013 -Idle contact switch, bad contact

I had just replaced the wiring harness, these faults came up with another air mass fault, I checked the afm readings at an idle an the flow rate kept dropping off to zero. I replaced the air meter, now the air flow shows steady, but the idle still flucuates, accompanied by a raunchy exhaust odor.
Is the "idle switch" part of the throttle unit in this application? The manuals I'm using (Mitchell) does not go into much detail on where to go next. I would much rather fix this with some friendly advise from those who have delt with this before than to chase my tail for days.
Thanks, Dan

Your getting the fault codes from where - the built in LED? And the descriptions are coming from Mitchell? Have you built the code reader for the other pins? I'm all questions.

I am using a Lauch x-431 to read the fault, the descriptions are from the same. Thanks

Go into EA/ISC/CC systems then go to data stream and look at throttle angle. If throttle angle is fluctuating with idle surge you'll need to replace or rebuild the throttle assy.
Mike

Thanks Mike,

I just found out the air mass sensor I bought is bad. At idle it showed
500kg/h , I removed the sensor from the housing and covered it with my hand, the flow rate dropped to 25kg/h (it should have read 0) and the idle smoothed out. I should have another sensor tomorrow.