Trying to resolve a CEL on my 1998 2.8 A6 I pulled an O2 sensor fault at B2 S1. While troubleshooting I found the connector disconnected and so figured I found the problem. Started the car and tried to drive it and it barely had the power to get back into the parking space After putting it back in park I noticed the idle fluctuating rather severely, it also smelled very rich, no black smoke but a distinct gasoline odor.

At first I thought I must've knocked a hose or electrical connection off so I checked and also re-disconnected my O2 sensor and it ran better Although it's running better disconnected it is still hunting for proper idle a tiny bit and is also getting horrible mileage.

Does anyone know what this means?

The O2 sensor obviously didn't disconnect itself so I'm assuming it was left disconnected by the shop who replaced my tranny. I seem to recall the CEL light coming on about the same time. Anyhow, since it runs worse I must consider if someone left it unplugged because there is something else wrong rather than merely forgetting about it. Also, along these lines, maybe they jacked something up while doing the tranny and didn't want to admit it.

Any ideas?

I'm trying to clear the CEL so I could sell it and prefer not to spend anymore than I need to. Any help is greatly appreciated.

 

Just finished testing all 4 O2 heater elements. All 4 tested at about the same 5 ohms so they (the heaters) should be good from what I understand. I plugged the sensor back in and the car is running better (but not great), wondering if maybe the sensor is fouled from being unplugged for so long.

Also, before re-trying it I noticed pools of gas behind each exhaust, it was literally dripping gas and blowing it out the pipes!

 

Plugged sensor in, reset ECM, car running great!

 

It is good you figured out the problem! With out any replies to your post.I have a 2003 a6 that I just got.I hope I dont have problems with the sensors getting fouled.

 

Thanks for the reply Gman, I was disappointed I never got a response but then again it is probably because others have never ran across what I was experiencing.

Congratulations on your purchase, if you do your own work Audi's are not bad, if you let others do the work beware! The costs will be high and unless you go to the dealer (more money) the work will be questionable. I recently (since this post) changed my valve cover gaskets, like many things Audi, it was harder than it should be but not too bad. The dealer would have likely charged me $1,000 but I did it in a few hours for $61. Another problem I fixed was the ABS module, dealer wanted $2,000, I had mine rebuilt for $45 and put in about 1.5 hours!

I figured I might as well update this in case others run into the same problem in the future. Apparently I simply needed to let the car run a little while before the sensor cleaned itself.