WICKIDSIX

Working with an 2002 z28 a4 mostly stock. When I bought the car a year ago the seller said that the cats had been gutted and he had o2 sensor simulators installed. After looking at everything he did not purchase the simulators that plug into the factory harness. He had cut the purple wire(data line) and hooked a wire to the pcm side of it. He did this to both rear sensors. Then both wires run into the car on the drivers side. Not sure where they go mainly cause I havent ripped up the carpet yet to find out. The ses light has never been on. When I changed the oil one time i noticed that one of his wires had come loose(still no ses light) So I hooked it all back up how it was from the factory.(still no ses light). Drove it like this for 6 months. I started to get a smell like it was running rich so I hooked his wires back up. didn't really make a difference with the smell. So right now his so called simulator wire is hooked up. Over the weekend I raced a buddy that I run all the time. I always beat him however this is the first time since I hooked the wires back up. I lost and the car didn't feel like it had as much out of the hole and felt slugish. Any opinions. I'm starting to think that it was running better performance wise with it hooked up like it was at the factory. Sorry for the long explanation but any opinions would be welcome. Thanks

Deviant LS1

iTrader: (4)

The rear oxygen sensors just check for emissions. They don't manage fueling.

180ls1

iTrader: (4)

this is true.

garygnu

undo his wiring and fix the harness,and delete the rear O2 sensor.

X-ray

iTrader: (6)

Running rich has nothing to do with rear o2 sensors though. Maybe the front o2s are going bad.

Damian

iTrader: (89)

Solid suggestion.

Once the harness is fixed, ditch the simulators and get a real tune. There are some reputable vendors on the site that offer fairly cheap mail order tunes that'll pick up some power and delete ALL of your emissions stuff as well. Simulators are known to go bad over time. A base tune is good for the life of the car.

WICKIDSIX

Thanks for all the opinions. The tune idea had definetly been in my mind. We have a local shop that from what I have been told is damn good plus they can put it on the dyno too. I am fully aware that rears are for emissions and catalytic efficiency, just wasn't sure if the way the simulator was done could be causing a problem. Thanks again the wires are coming off.