About two weeks ago my MIL (check engine) lamp went on about a day after a gas fill up at a non-self-serve station in NJ (state law prohibits self-serve in NJ). I use my trusty VAG-COM to determine the the fuel mixture is two lean on both engine banks. I figure the gas cap was just loose as in often the case with MIL lamp stuff. I tighten the cap and clear the fault code.

The next day, the MIL lamp comes back on with the same fault code so I make an appointment with my local Audi dealer.

Yesterday evening during my ride home, the MIL lamp goes out! Since the code is gone, I'm sure the deal will say "there's no fault so nothing to fix". I know if I cancel the deal appointment, the MIL lamp will "know" and turn back on.

Opinions needed:

Should I cancel the dealer appointment and hope the MIL lamp stays out (I did print the VAG-COM fault report) or should I take the car in, hand them the fault code and say "figure it out"? Any other options would be helpful.

I have a word document for my car, I save the date and codes in it before I clear anything.

Certain fault codes will clear themselves after so many repeated starts without them present. This is obviously one of those codes.

Did you subscribe to the online Bently manual at bentlypublishers.com? If so, you could find out what the possible problems are.

I would cancel the appointment and wait for it to come back on again, especially if you vag-com it and it's gone....the dealer won't be able to do anything for you.

BTW, fuel mixture too lean in each bank on the D2 A8's have been from a vacuum hose being off a pilot valve or due to a leak in the fuel tank o-ring.