Looking for some advice here -
2001 A4 2.8 Q. 100K (recent timing belt, pulleys, waterpump, etc changed 2 months ago)

I was way short on cash two weeks ago and put 87 octane fuel in instead of the normal 91 I use religiously in my car. One half tank, that's all. The check engine light came on, and when i filled the next tank with 91, it went off. However, now every time my gas gauge is between 3/4 and 1/4 full, the light comes back on - then disappears when the tank is close to fuill or close to empty. I am planning on getting the codes looked at, but can one lousy half-tank of fuel mess with the computer that much? I won't need a new fuel filter, will I?

thanks
patrick

 

I'm betting you got that gas at a station OTHER than your usual. I don't think it was the low octane of the gas you used. Yur car is more than smart enough to compensate for THAT without coughing up a lung. Now, the QUALITY of the low-octane gas... Possibly the tank (in the station) was low, and the pump sucked up some crap and dumped it into your tank. Or, you were lucky enough to hit the station right after THEY filled up, and crap in the (stations) tank was swirling around and got sucked up into the pump and dumped into your tank.

That's my take, anyway...

 

it shouldnt, i have, had, a 96 2.8 that my dad put 87 in, almost half tank, light came and i simply bought a code reader off ebay( a must for any B5 owner in my opinion) cleared the code, just the knock sensors going off and then filled up fully on shell v-power and some octane booster. same thing happened a few months later and i did the same thing only filling up with lead free race gas.

 

Try a fuel additive from your local parts store, something with techron, about $10. Should clean out fuel delivery system if your problem is only some kicked up garbage from the cheap station.
Good Luck