Catalytic Converter

The 2006 TJ 4.0 has (3) catalytic converters (2) on the manifold and (1) above the transfer skid plate. Does anybody know if the 3rd cat is really required to pass emissions inspection in RI. Some sources say its only needed to pass smog in California but all wrangler were provide with it. It is not monitored by the computer so I should not get a check engine light. I am just not sure if the inspection looks at the tailpipe emissions or just the ODBII port results which should be fine. With the rear 4-link I need a spot for a muffler. Maybe ??

Is it better to run (3) cats and no muffler OR (2) cats with a muffler above the skid plate OR (3) cats and try to find a spot for a muffler above the 4-link.

Jeff, I know one member who cut out the 3rd cat after he did a universal crossmember on his 05 TJ. No known issues to the best of my knowledge. I am also doing the same thing to my 03 TJ. They plugged into the obd2 for codes when I did my last inspection on January 2020. Now, they take 4 or 5 mandatory pics. One of the dash with the vehicle running, front and rear plates and one through the driver’s side window. Plate shields are not allowed and they will fail you for having them.

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Thanks Anthony. I leaning towards removing the cat so I can get the muffler above the skid and just run pipe to the rear of the jeep.

Technically speaking, if you alter ANY part of emissions, it’s grounds for failure in our state of RI. While inspections stations aren’t taking pictures beneath vehicles as of yet, they are of just about everything else. Are you friendly with any station?

I omitted my 3rd CAT on my 05 and have not had any CEL’s as the O2’s only monitor the pre-cats like you describe. However, I did feel a slight loss in torque sub 2,000 rpms which I’d say attributes to the loss of back-pressure.

I have an 06’ and have delt with exhaust issues from day 30… lol. You can eliminate the third cat with no issues. The problem you will run into is that the exhaust hanger is attached to the cat body and if you eliminate it, it puts extra stress on the exhaust. I hollowed my cat out and reinstalled it. I recently had to redo my exhaust for inspection because i was getting a check engine light. Come to find out, the flanges from the cats to the manifold had split and were allowing fumes to escape. I still have the old cat body if you want it.

My bighest issue now is that i cant keep the bolts tight that connect rhe cats to the manifold. The middle ones keep coming loose and setting off my computer. I have tried everything to keep these tight to no avail. Just dropped me.into limp mode today despite a brand bew system from front to back.

Thanks Derick… I don’t mind keeping the cat just not sure how to get an muffler in with the rear upper triangulated 4-link. I read a lot of post about mounting the muffler above he skid plate in place of the cat and just running pipe out back. that was my original thought. I’m gonna take it to an exhaust shop and see if they can make some thing work.

Jeff Clayton Offroad does the same thing for their TJ 4 link long arm kit. Everything moves forward and out of the way of the long arms.

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