i get crappy mileage on my 1999 a4. i'm assuming its the fuel filter and i think i found it, but i'm not sure.
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1999 Audi A4 Quattro Question: where is the fuel filter located
Answer #1dandd January 04, 2011, 15:16Master
If the fuel filer is plugged, you would very likely have a Check Engine Light code P0171 for a lean running engine. which would not effect your mileage, because the car is starving for fuel, not feasting on it.
The filter is back by the right rear tire, sometimes not real easy to do.
I would check the Long Term Fuel Trim, in your power train data. If it is negative, then you have a rich running engine which will cause poor fuel mileage.