This is kind of a newbie question but..I just recently put on a test pipe on my evo which just has an hks exhaust, dp, intake and intercooler piping, and i was wondering if anything bad would happen if i didnt relocate my O2 sensor. I know my car would throw a cell, but is there anything else that would happen? like fouling the O2 etc...Thanks for the help.

 

I asked a similar question a while back, I was told that the rear O2 is just for emissions not for tuning or AFR. So you will get a CEL, but you can just have your rear O2 turned off when you get a tune or try the mechanical CEL fixes. GL

 

thanks...but what if i decide not to do a mechanical cel fix? would anything bad happen besides my car throwing a cel?

 

Removing the rear o2 sensor (or modifying it in any way) won't affect engine performance at all if that's what you're asking. Everything will run the same as it did before. The only problem is you'll have trouble passing smog tests.

 

i see...well i have my stock cat and if i need to get a smog test, ill just put it back on..If i disconnect the rear O2 sensor, will i still get a cel?

 

Yes. That sensor is there to make sure you have a cat that is functional. Removing the sensor is the same as having one that does not work, and should throw a CEL. If you have a bung, just go to a car parts store and get a spark plug anti-fouler to pull the sensor out of the exhaust stream. Then you can keep the sensor working so it will not throw a CEL. But again, it is only for emissions, and will not affect performance in any way. Front O2 is a whole other story though...