Check Engine light Funny business? - PeachParts Mercedes-Benz Forum

david s poole · #1 06-05-2007, 09:50 AM

your maf could be running lean at low rpm's[2500] which might explain the good gas mileage.you will need to scan the live data and see where the adaptions are before going any further.

blackmercedes · #2 06-05-2007, 11:21 AM

There is no such thing as a code that specifies the Air Mass Meter is faulty. There is a fuel trim code that will point you in the direction, and then you use the adaptation values to get closer. Also, cleaning an AMM is usually a temporary fix at best, and replacing the component is typically the only way to ensure the fix is done properly.

Pull the codes, read the values and get a proper diagnosis going.

Since you have a known-good AMM, you should read the fuel trim adaptation values with the old AMM in place and then again with the new AMM.

G-Benz · #3 06-05-2007, 05:11 PM

Since you went the "clean the MAF" approach, have you gone ahead and changed the air filter as well?

Designo_E320 · #4 06-05-2007, 06:48 PM

Quote:

Originally Posted by G-Benz

Since you went the "clean the MAF" approach, have you gone ahead and changed the air filter as well?

yes

#5 06-06-2007, 03:10 AM

Quote:

Originally Posted by david s poole

your maf could be running lean at low rpm's[2500] which might explain the good gas mileage.you will need to scan the live data and see where the adaptions are before going any further.

I had the same thing happen on my Northstar('97 Eldorado), the lean mixture caused a bad case of pre-ignition. The live data feature is invaluable on scanners, it's paid for itself after two repairs.

A rebuilt MAF from the dealer was $130, throttle response was much better with the new one as well. It took me longer to drive to the dealer and back than it did to do the whole repair, including two test drives.

david s poole · #6 06-06-2007, 09:49 AM

your e 320 fuel injection computer has the ability to modify the mixture by 30% in either direction.this is called adaptions by mercedes.your cel is probably coming on because it has adapted to the limit[either rich or lean].until you replace the maf this may be an ongoing experience.