(I apologize for the lengthy post)

I have a 2003 A6 Avant 3.0 with 80k miles. I've owned the car for about a year and a half and it has had the check engine light on since about a week after I bought it. I had the codes run and it's for two oxygen sensors, but every VW/Audi I've ever owned (5 Audis, 4 VWs) has needed oxygen sensor and every VW/Audi mechanic I've ever talked to said it's not a "must fix now" sort of thing.

Anyway, periodically it doesn't start. The starter is clearly cranking, it just won't start. Naturally, it won't repeat this for a mechanic and usually if I let it sit for a day or so, it will start the next time I try it. After being unable to get the issue to recreate for my mechanic the first time, he advised that I just push the gas pedal all the way to the floor when starting it after it gets moody. When I did this, it would start after 15-20 seconds, idle really rough and uncontrollably for 5-10 minutes and then everything would be fine.

In addition to all of this, about 60% of the times that it starts fine, the battery light comes on and the car is sluggish for the first 2-3 minutes and then the charge goes up to where it should be and everything is fine.

I've had the battery tested, it's fine. I've had the connections tested, they're fine. I've had the alternator tested, it's fine. My mechanic replaced the belt that runs the alternator and I'm still having the problem.

Now, today, the gas pedal to the floor work-around isn't working and my car is stuck in a 2-hour parking place downtown just waiting for parking tickets. Ideas?

 

Chances are pretty good that your mixture is screwed up and guess what the O2 sensors do? There is also the MAF in the mixture, and a failing fuel pump or clogged filter. Then there are the injectors. Whatever it is, it's probably the fueling system. Be careful with bad O2 sensotrs, they can take out your cat converter, expensive....