I've got a bad O2 on the front drivers side.

Does this affect performance?? Does the computer pull timing to prevent damage with a bad O2? I've got one ready to go in, but I just want to know if I might expect a performance increase with the new one.

 

your gonna make the car run correctly

performance, maybe but only performance you have lost due to having a bad sensor

the computer uses the front o2s to regulate fuel

 

I know that your car uses default values for 75% throttle and up (128). In other words your 02's affect your gas and part throttle more than your full throttle performance.

I believe that your timing gets pulled when you have false or real knock only.

I say change it out as soon as possible. This why scan programs are great, because you get to actually see what is going on.

 

Not completely true. The PCM uses the long term (learned) fuel corrections stored in Cell 15 when it goes into power enrichment (PE) mode. It can go into PE mode at throttle positions as low as 38% at 4,000rpm, and 28% at 5,600rpm with the stock programming. It uses the Cell 15 long terms for fueling when the PCM has been adding fuel in that Cell in closed loop. Hence, if the PCM "learns" the wrong long term corrections in closed loop, due to a faulty O2 sensor, that error will be carried over to the PE mode (WOT) fueling, and screw it up.

The exception is when the long term fuel corrections are subtracting fuel in closed loop, the PCM will default to Cell 15 or Cell 18, but lock the long terms at 128.

Short answer - faulty O2 sensors hurt your performance. Fix it.

 

Having a bad O2 does affect WOT performance like Injuneer said. In laymans terms I think he is saying that the computer will learn a new fuel curve based on the faulty O2. So the fuel curve is all whacked due to bad O2 readings in closed loop and it will carry over into WOT as well.

 

Does diconecting the negative terminal for a while reset the computer?

 

Not if you are tuned, any good tuner tunes out that feature.

 

Not that Injuneer needs back up, but yeah he is right. It happened to me from an exhaust leak causeing really bad LT fuel trims.