Step-son's big prix

[GRR8APE]

My step-son has an '07 Gran Prix with a cute little 5.3L. The motor is just turned the wrong way! Seriously... He has a electric cutout in place of the cat. This means no O2 sensor. He thinks this will not effect anything except for the dummy light on the dash. Is he correct? I think having no O2 sensor at all would cause some fuel trim issues. Please help us o'wise one.

[GRRRR8]

It will effect catalyst efficiency and set a code unless he has turned off the rear O2. It wont effect the front O2s.

[GRR8APE]

So just a re-tune to delete rear O2? By-the-way the cutout is in place of the cat, so no cat at all. He is trying desperately to catch me.

[usf3983]

He is trying desperately to catch me.

im not an expert, but that seems futile. could get expensive.

[dispatchg8gt]

If the cutout is before the first O2 it will screw with his trims at WOT. Engine goes open loop at WOT and bases fueling off what the first O2 sensor reads. If the car ain't seeing flow past the first O2 bad shit could happen.

DISCLAIMER: This is based off my knowledge of the 3800 series III in my 04 GP Comp G.

[GRRRR8]

If the cutout replaces the cat, just get it tuned to turn off the rear O2(s)

['02 ws6]

Or buy some 02 simulators.

[JP GXP]

The car is mine. And so all I have to do is tuned out the rear 02 and that's it?

[Darkside]

Not sure you'll gain a whole lot from it. Any other exhaust upgrades? Might get a little stinky as well.

[done12many2]

The car is mine. And so all I have to do is tuned out the rear 02 and that's it?

Have the rear O2 sensors disabled in the tune and retune for the cutout. It should sound terrible! Good luck with the project.