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Air pump self test. Normal. Didn't we have this conversation already? Turn your caps lock off, it's annoying.
If the car experiences a 1-2 second dip in the idle, with a "shudder," then runs fine the rest of the time and no CEL, then what you're experiencing is the air pump self test. I've owned my C230 since new, for 240,000km now, and it has done it since new, and always will as long as the air pump is working properly.
You can keep throwing time, money and effort at solving this problem, but I doubt you will ever be satisfied. The car has a normal system operation that causes a slight idle drop. Get used to it.
Don't clean the Air Mass Meter. You're asking for trouble. They were not meant to be serviced, and even if it was failing, at best you bought a little time. The failure of the AMM causes a fuel trim adapation problem and is easy to diagnose. First, 95% of the time it will throw a CEL then you'll have a terrible hesitation at 4500rpm and above. Driveability will be effected.
Now that you screwed with the AMM, I'll bet that sometime in the not-too-distant future it will go out on you. If you get code P0170/P0171, then have the adaptations read and I'll bet they be maxed at 1.32 and you'll need a new AMM. BUT, the symptoms are different than what you're describing.
Last edited by blackmercedes; 12-15-2007 at 01:46 PM.
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