Hi, my first post in this section but anyway....
I recently got a 2003 A4 3.0 Quattro (Auto) and every time my tank goes about half empty/ almost empty my check engine goes on...I took it to the shop and checked it out it had something to do with the fuel, this is the 4th time it has came on, i erased the check engine the past 3 times but every time i get almost an empty tank it goes back on...any ideas why? I also fill up on Chevron 91 and only on that gas. I dont mind the check engine but it bothers me....My theroey is that the people before this filled up on the cheapest gas (car has 82k miles) and maybe the car is somehow thinking the fuel is bad/wrong? Thats my theroey about it but im probably wrong...

I was also wondering what are your opinions on the B6 3.0 Quattros? Are they good cars? Fast compared to the other models? I changed the T-belt and all that type of annoying stuff Audi's are infamous for...

 

what code is it giving?

 

I bought a 2003 A4 3.0 MT6 with 69k miles and now have 82k. It needed brakes and a battery when I bought it -- I knew that by inspecting it myself. When I brought it in on the coil "recall" I found the coils were good but the catalytic converters had to be replaced, fortunately under warranty. Lately I have had an annoying CEL due to the clutch position sensor (replaced once and needs to be done again) or a camshaft sensor (scary, but it cleared and has not come back, replaced by the cps). Annoying, but it's a great little car otherwise. In some ways, more comfortable and a better form factor than my A6. It has plenty of power for my 18 year old daughter, but it is not fast like my 2.7T.

 

try checking for pressure in the gas tank. its either you need new gas pump or new cap. I had that problem replaced the cap and it worked fine. Do you have a car and a gas showing on your dashboard when the gas tank goes half empty or just a check engine, or both?

 

The check engine goes on when the tank goes half empty, and almost empty. After a few hours of annoying electrical work i found out my car has eletrical problems and needs a new catalyic converter...

 

Do you have the P0420, P0431, P0421 codes?

The first one is the EVAP system thing, which could be caused by a small leak on the fuel system (gas cap suspect) and the second two are the Catalytic converters.