Are rear o2 sims required with an aftermarket x-pipe?

lowered99gt · 07-07-2006

I was curious if rear o2 simulators are required with an aftermarket catted x-pipe. I've been trying to diagnoise a very rough idle, and lack of power on my 99 GT for a long time now. It has an aftermarket (UPR i believe) catted X-pipe. The car ran great when i bought it about a year ago. Two weeks later the Check engine light came on, and it was diagnosed to be bad o2 simulators. The shop gave me a set of 03 cobra oxygen sensors, and the car has been slowly running worse ever since. Stumbling upon accelleration, and acting like it can't get out of it's own way once it warms up.

Are o2 simulators required after installing an aftermarket X-Pipe, or are they only needed if the light comes on? Would they cause the above condition without a check engine light?

BlueStreak03 · 07-07-2006

Yes, you need the O2 simulators or MIL elimintaors when running an offroad pipe unless you get the rear O2 sensors turned off in a tune. When I had an offroad pipe, I noticed a distinct difference once the CEL came on.

sc2000gt · 07-07-2006

It says he used a catted midpipe so all four O2 sensors should have gone back on. Are you sure they are connected right? Are you sure the replacements were good?

As stated, you could always get a handheld tuner and turn them off. MIL eliminators can go bad too.

BlueStreak03 · 07-07-2006

I had to install MIL eliminators even on a catted pipe. The high flow / low efficiency cats can sometimes still give you a low catalyst efficiency code. I wouldn't say that turning the rear O2's off with a tune is my preference, especially if you live in an area where an OBD scan is done for emissions. You may still fail the scan if the rear O2's are turned off.

lowered99gt · 07-09-2006

I'm not getting a CEL code using the rear o2's. I just wanted to know if using simulators in place of the o2's would get rid of the stumbling and serious lack of power I'm experiencing. If the o2's don't fix it, I guess it's the PCM, and I'll have to get ripped off by the dealer. $125 to program a second key, just so they can program the PATS system to my other PCM.