I've got a diagnostic question regarding my daughter's 2000 A4 1.8. <i>I've posted it here because I trust the collective wisdom of our TT crowd.</i>

Anyway, her car will idle smoothly but when trying to drive, it experiences misfires on all cylinders and as a result feels dangerous to drive. I scanned it with my ProDiag and it shows a series of DTCs, most prominantly: 16684 P0300 035 (Random/Multiple Cylinder: Misfire Detected) along with 16688 P0304 035 (misfire detected for cylinder X) for each individual cylinder. So it doesn't seem to point at any particular coilpack--misfires seem random and spread over all cylinders.

Suspecting a bad MAF sensor, we attempted a full-throttle run in 2nd gear (which was difficult given the car's uneven throttle response). While attempting to floor it in 2nd gear, <b>block 002</b> showed the air flow never exceeding 41 g/s even at 5900 rpm (it should have peaked at about 120 g/s for this 150hp engine) and <b>block 032</b> showed the part throttle O2 adjustment pegged at +25% (I believe these should be +/- 10%). The full-throttle run also caused this additional DTC: 17536 P1128 035 (Bank 1 Mixture Adaptation (Mult): system too lean) which confirms my block 032 numbers.

I wanted to disconnect the MAF sensor to drive it on it's default fuel maps, but the MAF is buried within the air cleaner and if you've ever tried to replace the air filter on an A4, you know it takes 3 people and a rocket propelled grenade to get inside that infernal contraption. The most mechanic-unfriendly design I've ever seen.

<b>So, what's the general consensus?</b> Bad MAF causing the multiple misfires? The car is just within the 7yr/70k miles extended MAF warranty but we'd like to be pretty certain before heading off to the dealer.

Additional info: one of the O2 sensors was replaced a while ago, and the secondary air pump was just replaced (we think this was happening before the air pump job but the new driver wasn't telling us).

TIA,
~john

 

The G/Sec and partial throttle numbers BOTH point to a bad MAF. The ither faults are probably related to that...(not enough fuel)

 

Otherwise I would say you are right on...
you can read 211 to compare actual &amp; requested MAF

 

an access hole makes sense, though.

Thanks.

 

Thanks Steve, that was my suspicion.