hello.. sorry for my English is not good enough, but I'll try to explain the problem. I own 98 2.8 30V audi a4 quattro with a 85k mileage. I am getting 11mpg driving smoothly in the city and it's way too little.. I have just had a full engine check.. repairer regulated MAF sensor, because the RPMs was shaking a bit, also he found that air bolt were stuck, so now the car is runing fine, service computer shows no errors, but the fuel problem remained the same(with 16 gallons I run 180 miles). I know that o2 sensors are working fine, spark plugs are fine, fuel presure is as it should be, nozzles are clean. Could it be the timming belt fault??? any other suggestions? thanks for your help..

 

how do you know the O2 sensors are fine?

 

o2 sensors were checked on VAG, it showed that voltage of sensors was changing between 0.2-0.7 volts. Could o2 sensors anyway be broken-down??

 

Sure just because they appear to be working fine doesn't mean they are. It takes a lot for the CEL to trigger due to O2 sensors.

 

I am quite sure o2 sensors are ok, I checked them in several garages and there are no others symptoms exept fuel economy that o2 sensors are defective. RPMs is stabile and the car is accelerating quite fine... is it posible that just one of o2 sensor is working and another is corrupted and I can't notice it then I am driving?

 

Anything is possible...how many miles do you have? They usually decrease fuel economy around 70k miles.

 

I have around 85k miles..