I posted this in OEM too but it kinda straddles the line. The question is: Could using a BFH to loosen the exhaust pipe cause 02 sensor damage or anything else to cause severe missing?

Installed the Dynomax catback today. The old muffler was seized on the cat so I tried lots of PB and a BFH to no avail. I ended up prying the old muffler flange off and shook it loose from the cat. There was a fight, for sure.

During test drive there was a bit of smoke, which I figured was normal. Then the engine started missing pretty bad. It would miss intermittently and then have full power for a while before missing again. I tested again a couple hours later and no smoke, but same intermittent skip. The RPM's are all over the place.

The system bolted up great and the extra oomph is obvious. The 02 looks ok and connected, EGR never acted right, but this engine never missed before either.

My guess is I knocked the 02 loose or something. Will that cause such a symptom?

 

You could try disconnecting the downpipe collector from your header and see how it runs with open headers. If it runs fine you know you have bad o2's or a clogged cat.

 

CPS wire was touching the front pipe and almost burnt through.