Exhaust O2 Sensor Error

[2010S4]

So a couple of days ago I was at my dealer getting the 5K service done and me and the service rep were talking about mods to the car. He is cool with me changing things on the car, which I was surprised about. OK, now onto the real question. I told him I want the Milltek exhaust for my car and he said that it should sound great but he has seen problems with people having problems with their O2 sensor. He said that where the sensor mounts does not line up right on the S4 with the Milltek exhaust and this causes a fault to be tripped. Has anyone with the Milltek exhaust on their B8 had this problem, or even with any aftermarket exhaust. I am thinking that maybe he was talking about an older model S4, but I am not sure.

Thanks

[NWS4Guy]

BS.

The O2 sensors screws into the Cat, there is nothing at all to do with the Milltek or any of the other aftermarket exhausts out, as they start at the back of the cats, hence the term Cat-back. Possible he was talking about older models, as it's definitely not an issue on the B4 unless you are messing with replacing the cats.

[2010S4]

Ok, thanks, no I am just getting the Milltek exhaust, not planning on messing with the headers.

[Dubber4life]

I think he may have been thinking of the B7 RS4. From what I remember there was an issue with the Miltek downpipes putting the sensors in a location other than stock causing some problems.

[NWS4Guy]

Ok, thanks, no I am just getting the Milltek exhaust, not planning on messing with the headers.

OK, but know that the headers and cats are seperate. On many other Audi's there are:

Headers + Downpipes (which have cats attached)

B8 S4 has: Headers + Cats + Downpipes (which is a seperate piece entirely from the cats)

[2010S4]

OK, but know that the headers and cats are seperate. On many other Audi's there are:

Headers + Downpipes (which have cats attached)

B8 S4 has: Headers + Cats + Downpipes (which is a seperate piece entirely from the cats)

I see what you mean, well I am just getting the cat back system so there will be no changing of either the cats or the headers, so i will be all good. Right?

[JMN]

This gives very good idea what our systems looks like....

[compguy]

I have a stock car and for my last service was told that the O2 sensor had logged an error in the past but wasn't erroring at the time of service so it wouldn't be replaced.

[NWS4Guy]

I have a stock car and for my last service was told that the O2 sensor had logged an error in the past but wasn't erroring at the time of service so it wouldn't be replaced.

Yes, it can happen randomly at times. They have tight thresholds in regards to the amount of airflow and tumble, as well as how long they have to reach operating temps after startup, it's also not unheard of that they can fail at times with no cause - it's a part like others (water pump anyone?) which can fail sometimes.

[Alkivar]

the solution for O2 sensor codes is simply a spacer for them...

you want some of these to solve the problem: http://store.42draftdesigns.com/O2-S...cer_p_306.html

[StratJohn]

^ yeah but on a stock car, thats more something a dealer should handle or look into as it may imply an error that -should- be handled by warranty.

None of the aftermarket systems affect O2 sensor performance for this car, so everything should be fine.