I took my car to the track for the first time the other night and I got 3 runs in. I have a 99 WS6, bone stock except for a lid and cutout. Car seemed fine after first run but after the second run it started to idle a little funny. By the time I got my third and final run in and was leaving the tracks I saw that my service light came on. I pulled over in a gas station, checked the car and reset the computer. After doing that the service engine light went out but the car started idling really funny. It almost seemed like it was going to stall, it'd dip to about 500 rpms. After letting the car sit for awhile I fired it back up and it ran fine. I friend of mine later hooked it up to his code scanner and found that there were no codes however he said looking at his data he thinks I have a lazy drivers side rear o2 sensor. Does this sound accurate? Should I replace the o2 sensor with a factory GM part or are there any aftermarket o2 sensors?
Thanks for your help guys,
-Kris

 

When you say rear do you mean behind the cat? Do you have the exact O2 sensor label he was looking at?

The o2's behind the cat's (on the muffler side) shouldn't affect performance. They just monitor the cats and make sure they are working properly.

They are pretty expensive so I wouldn't change it unless I had too.

Eric

 

The rear o2 sensor wont cause performance issues but can throw ses..the running rough after you reset computer is due to it relearning..that is nothing to worry about..

-Dave