A few months ago my left cat began to rattle BAD. I got on it pretty good one day and the rattle stopped but the check engine light came on. I assumed it blew a chunk out and jacked up the rear O2.

I got an off-road y-pipe from Jegs with no cats. I reinstalled the old front O2 sensors and I plugged up the rear O2 sensor bungs and left the sensors out. Of course this leaves the connectors open to the elements, dunno if thats a problem.

Minus a small exhaust leak at the mid pipe flange it started up and ran fine. Much louder than I expected but thats probably due most to that leak. I drove around until it was warm but when I parked it ran rough. I checked all the connections, all tight, replaced the front O2s with new ones, drove it around and ran great.

Drove to work with no problems. Drove home and when I parked it ran rough again! WTF. I have not had the check engine codes read since the light came on months ago. Any ideas?

 

Prob going to have the say the rear O2's are your problem...

 

From searching ive learned the rear O2s only measure cat efficiency and have no effect on air/fuel mixture, PCM control. That being the case I assume they have no effect on drivability.

I think im going to take it to the auto part store and clear the codes for now just to see what pops up. Im expecting codes for the rear O2s since the cats are gone.

Is it possible one of my new O2s is bad?

 

People install simulators or have them tuned out when they are removed, not just leaving the connector disconnected.

 

I terminated the wires and plugged the connectors back together. Everything runs fine now. Thanks

 

Leaving them unplugged would not make it run rougher than plugging them back in.

 

It will if water gets into the connector & shorts the terminals. I've been down that road before.