Not sure if they've proven to be problematic on the E53, but on my E39 M5 the MAFS (air mass meters just inboard of the air filters) were susceptible to fouling. The wires get coated with grime or dirt and don't work well at all. The intermittent nature of what you describe is what prompts me to think this.
Problem is, if the OBD doesn't spit out a related code (and it rarely points to the MAFS), then it's a b!tch to get a dealership to start looking there.
I fouled my own on the M5 by installing brand new K&N's the day before a track weekend at Road Atlanta (read: lots of Wide Open Throttle). Some of the oil that makes those filters function migrated onto my MAFS and I began to experience loss of power, hesitation, and operability issues.
Even when I directed my SA to start the diagnosis there (I brought in printed out pages from m5board.com detailing other members' similar symptoms) his and the techs' hands were tied by what the diagnostic computer spit out. I ended up taking it to another dealer where the tech used a voltmeter to determine the MAFS was putting out wild readings.
I've heard of dealerships swapping out the MAFS from another customer's car to help in their root cause analysis.
One other thought: some folks have done a DIY cleaning of the MAFS and report good results. You can find detailed write-ups with pix at:
http://www.louv.tv/cars/m5/MAF/
Good luck!
-Dave
06-08-2006, 09:35 PM
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