Everytime I fill up my TT with gas I get a check engine MIL - System too lean. I dont understand what the problem is. Is it with my gas cap or is a o2 sensor going out? The other day i experienced a great loss of power and then the check eng. light clicked on and my power was back. The light goes off about half way through the tank of gas.

Any ideas?

Anybody else getting these MIL's?

 

We generally refer to a Check Engine Light (CEL) rather than calling it a MIL. I did a little searching on Audiworld and came up with the following suggestions for a very similar problem.

1)Check oxygen sensor and oxygen sensor control before and after catalyst

2)Check fuel pressure regulator and residual pressure

3)Check mass airflow (MAF) sensor

4)Check intake system and vacuum lines for leaks

5)Check fuel injectors and EVAP cannister purge regulator valve output

6)Check air intake screen(if equipped) and air filter for blockage. [have you changed filter?]

7)Check exhaust system for leaks [do you have cat-back?]

8)Check Secondary Air Injection (AIR) system for leaks (if so equipped)

You have to knock these off one at a time, not necessarily in the order shown. To check your MAF try unplugging it and driving. If the MAF is bad you should see a regain in power (unplugging MAF forces ECU to use the default map). The EVAP cannister may be the source of your CEL when the tank is full.

Do you have access to VAG-COM? If so, do a 3rd gear WOT run from 2000-6000 rpm while logging block 032, that will give an indication of the MAF function.

 

Ok, well it happened again yesterday. I have had two CEL's in one tank of gas. I am also getting really good gas mileage. If I take the car to the dealership, because it is due for a 30k mile checkup and i will have them check this problem out, would they be pissed at me for having it chipped?

 

Did you have it flashed or a new chip soldered on? The dealer can't tell from their scanner that there is new software running, the only tattle tale would be if they drove it or opened up the ECU box itself.

 

It could be a ton of things. You should take it to get the codes read and that could narrow it down a little bit. I had the same issue and it ended up being the CATs and the Mass Air Flow Sensor. I am having all the O2's replaced on Thursday too.

 

I just had it flashed. Ok, good to know that they wont know unless they drive it. Cool. Thanks for the help. I am getting it checked out next week. Hopefully the problem isnt to $$$ hungry.

 

I'm not too sure how many miles are on your car but Aud will cover the CAT's up to 68k without a warranty. Do you have an extended warranty? If so, it should cover just about any emission problem. I have had over a grand of work done on mine and it has all been covered. Let us know the outcome. Hopefully it all works out.

 

Wow... good stuff. The less & I have to spend the happier I am. I'm just a broke college kid and all my money already goes into this car.

By the way, my car has 29k miles. Should be covered.... I hope!