Comptech and 02 Sensor

[FailureToStop]

I recently had a problem with a wire getting unattached from the cat which resulted in the check engine light (CEL) to come on. If the race header from Comptech gets rid of the cat, how does Comptech get rid of the CEL?

[02SilverSiHB]

most likely they don't get "rid" of the cell, the just go on without it, or get a simulator for the cell. If the cell is on because of the cat being removed....I hear there are no losses in gains from this.

[chunky]

Originally posted by 02SilverSiHB
most likely they don't get "rid" of the cell, the just go on without it, or get a simulator for the cell. If the cell is on because of the cat being removed....I hear there are no losses in gains from this.

if you fuck with the primary O2, you will get a CEL that will trigger limp mode. The secondary o2 sensor is inconsequential - it will still trip CEL but won't put the car in limp mode.

The most obvious solution to installing a longtube header in the EP3 is to move the cat farther downstream. All you'd have to do really is cut the wiring harness for the two 02 sensors, extend the wires, reattach the wiring harnesses, then install the cat where the silencer in the stock midpipe went or something. Startup emissions would be a concern, but if you wrap the header & midpipe, the cat would heat up not too much slower than stock and should still get up to temperature.

[FailureToStop]

I posted this on another thread, but I guess EPhatch's software wasn't taking it or nobody was interested. But...

I drove around with the CEL light on for a week (the CEL came on due to the 02 sensor being unplugged from the cat by me bumping a rock). Don't know if it was the primary or secondary wire (dealer fixed it) that was loose. But for that whole week I got an additional 1-1.5 MPG. This was also the same week that I drove around without a spare and only a can of fix-a-flat. So I wasn't too sure if the loose 02 sensor or the lack of a spare gave me the increase.

But this "limp mode"... maybe it was the loose O2 sensor that caused it.

Anybody want to try this experiment (unplug the wire on the cat) for a week and report to us any MPG changes? Anybody? ....Bueler?