Bad O2 sensors?...long...

[Blivit]

My car is an 01 with right around 40,000 miles now.

I installed a P1SC about 6,000 miles ago and had it tuned. Car ran great and made good power(365/382 at the wheels) Roughly 1 week after the tune, the car began to have trouble starting..seemed like it was bogging out. Then, the check engine light came on. 2 codes...system too rich. Seemed right...too much fuel on startup.

Went back to my tuner and he leaned it out some. Again, car ran fine for about a week then same things happen, bogging startup and CE light.

I went back again, he leaned it out a little more and put it back on the dyno....on one run, it was around 14 on the a/f meter at wot...ie really lean...and the CE light came on right after that saying system too rich.

So now my tuner thinks my O2 sensors may be bad. The car has never thrown any O2 codes though...only the system too rich codes...both bank 1 and bank 2. We originally thought it was due to the altitude differences. I had it tuned in north carolina...and I lived in virginia, high in the mountains. I recently moved to florida though and it is still doing the same thing.


cliffs notes: car is tuned, has trouble starting and the CE light is on...system too rich. Can this be the O2 sensors?

 

[Dark Knight GT]

With over 40,000 miles on the car, it is "possible" that it is the o2 sensors. However, I think what you're having is a programming issue. The stock computer is setup to look for trouble based on how the car runs whenever it is stock or near stock. When you put the supercharger on the car and go it tuned, you had to increase the fuel pressure. It could be that your ECU is just not adapting to the new programming and although its programmed to pump more fuel, it's not programmed to recognize this as a "normal function". You can try replacing the front o2 sensors and doing a basic tune up on the car to see if that changes anything but I think its a computer/tuning issue and not a physical problem outside the computer and programming.

 

[joeymatt]

Actually, oxygen sensors do not typically fail, but they are blamed for a lot of problems. However, given your circumstance (i.e. supercharger install - increased fuel supply), your pre-cat oxygen sensors may have been contaminated with fuel.
When an oxygen sensor becomes contaminated the sensor is no longer capable of sampling the exhaust (i.e. reading the exhaust gas oxygen) as it was designed. In this case the oxygen sensor reads no oxygen, returns a signal near 1 volt to the PCM (which the PCM reads as an extremely rich condition - 0 V TO .45 V = lean, .45 V TO 1 V= rich), and the PCM begins to lean the A/F mixture by lowering the pulse width of the injector. However, the PCM can only adjust to certain a point and beyond this point it illuminates the check engine light and continues to do the best it can.