Hello to everyone on audi forums, this is my first post on the website. I've had my 2001 s4 for over a year now and I love it to death. The only problem with it is that the check engine light has been on for the past few months; Now dont get me wrong here im not a negligient owner, I had it checked out and it seems one of the o2 sensors is blown in the car. I did notice it has been running a little rich lately and was wondering if this robbed me of any horsepower or not. The cars performance in the 3000+rpm range has not been affected at all but i was wondering if a blown o2 sensor could have any affect on the cars performance, or if its just my turbos on the way out(cars nutless under 2000 rpm). Any feedback would be appreciated. If the turbos are on their death bed than i might be better off getting rid of the car now and buying a new one.

 

A bad before cat O2 sensor can have a profound affect on gas mileage and engine performance. An after cat O2 sensor just reports the efficiency of the cat converter.

 

o2 sensors can affect your performance it affects the gas because they control the amount of fuel it can also cause a missfire because the amount of fuel it sends. and if your check engine light blinks dont drive it because it can screw up your catalytic converter,i cheap fix turn in to something big so get it taken care of also dont get universal ones because they dont work really,universal ones are the ones that you have to rewire yourself instead of connecting them to the connector here is more info http://www.youtube.com/watch?v=4G6LiALLOEc hope this helps

 

I drove my s4 for a while with an erroneous after-cat o2 sensor with no serious problems other than a little worse gas mileage

 

GET A VAG-COM! Then do some logs, & check the codes, yes, o2's can cause poor running, but so can a bunch of other things.