Question about the catalytic converter

If you don't need them where you are, you could get rid of them. but i think your engines pc would freak out and continually send codes, and cause fuel mix to be wrong.

I assume your TJ is a 4.0L? The O2 sensors only monitor the pre-catalytic converters, not the 3rd main converter; cutting it out won't make a difference to the PCM. I had the same code and replaced all the O2 sensors and got a replacement Flowmaster Y-pipe that included both pre cats and a main cat. I would recommend it, but unfortunately the price has shot up from ~250 to over 1,000. If I were in your shoes, I would wait and watch the price until it is reasonable again before replacing it.

I just bought a 97 TJ 4L 6 cyl and the PO said he cut the cat off and had a regular muffler welded on. I don't know anything about codes but mine seems to run fine and shows no codes. Gas mileage seems ok too. I also questioned if the computer would read things differently if the cat was not there and adjust the air/gas mixture differently. But like I said, I don't know much about it and it seems to run fine.

The upper cat is probably what is setting the code. I'd fix it personally but if you cut it out the Jeep will run fine. The real downside is the check engine light will always be on so how do you know when something else goes wrong?

CheechJeep said:

So I recently purchased a 2004 wrangler TJ, and the check engine light came on and the code read P0432, P0432 code means that your catalytic converter for bank 2 of your engine is performing below what it should be. Generally, this is a sign that the converter has failed, but the problem may be related to an oxygen sensor. ... The car's computer monitors converter operation and efficiency with oxygen sensors. What recommendations does anyone have I've been thinking about just having the catalytic converter cut out and replaced with a straight pipe, any opinions

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Check the bolts that attach the mini-cats to the manifold.
When I get one of those codes, I always find mine loose.

CheechJeep said:

I’m in Indiana and you don’t need the catalytic converter I’m just worried about the pc getting off and causing more issues

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You don't need them right now you mean. If you are watching closely the Feds infrastructure and stimulus bills have conditions if your state wants the money. I'm not saying it's a done deal, but the EPA is cracking down hard on internal combustion engines.

Really the best thing to do is unbolt the assembly and take a look at the catalyst in each of the converters. You will be able to see very quickly if it is damaged, plugged, or otherwise bad.

When my pre-cat went, it completely self-gutted and there was no catalyst left behind in the converter. It all blew out and clogged up the main cat.

If you have a few dollars to blow on a fancy tool, you can get a cheap camera probe for $20-50 that plus into a USB or phone. Insert that into the oxygen sensor hole, and take a look at the catalyst. That would save you the time and trouble of unbolting the whole assembly.

Only the two pre-cats are monitored by the PCM. Gutting either of these or installing one less active than factory will result in the PCM adjusting fuel/air to accommodate, unless it is otherwise tuned.

Gutting the 3rd cat will not cause any codes, nor will it help nor hinder power. Modern cats are very flow efficient and do not cause backpressure unless they are malfunctioning. Since this one is not monitored, the computer has no way of knowing the state of the catalyst. The only way a 3rd cat issue will cause a code is if it becomes plugged.

Tuner software can indeed disable all of the catalytic converter monitoring and prevent a CEL for gutted cats. As to how this affects fuel/air, it would depend on how the engine was tuned.

For both safety and ethical reasons, I run all three catalytic converters. They don’t hinder the power at all, but significantly reduce carbon monoxide and NOx emissions. This makes it much safer to be around, especially if it is just idling or running slowly with people standing around it. I also live in an urban area, and personally believe it would be unethical to unnecessarily produce NOx and carbon monoxide for the same reasons I find unnecessarily loud exhausts unethical.

FYI - If you do go down path of swapping O2 sensors, make sure you buy the right ones. You ONLY want the NTK ones. Here is a link https://www.rockauto.com/en/catalog...01,exhaust+&+emission,oxygen+(o2)+sensor,5132

The bosch or whatever else your local parts store will sell you are crap and will lead to codes/errors. I swapped all of mine the day I bought my LJ (the next day really, bc I got home at 3am but same thing)

Tob said:

I assume your TJ is a 4.0L? The O2 sensors only monitor the pre-catalytic converters, not the 3rd main converter; cutting it out won't make a difference to the PCM.

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I'm still relatively new to Jeep'ing, I didn't realize we had 3 cats though I've always wondered what the "extra" "muffler" was for. This is a good TIL for me. Thanks man.

OP, personal opinion here, but O2 sensors are not life of the vehicle item. If you think they're original they should be replaced. They're consumables and they get lazy as they age. I flip E46 Bimmers for funsies and the first thing I do is new O2 sensors. Those cars ECM's are so finicky with air/fuel ratio it's worth making sure it's accurate. Maybe our TJ's aren't as susceptible but I'm a big proactive maintenance guy especially since in a couple weeks your Jeep will be able to buy cigarettes and porn.

When I stuck a high flow cat on my Monte Carlo using a spark plug non-fouler got my cat light to turn off. It's a super cheap, low risk option to try perhaps.

Do you happen to have a code reader? Not to burst your bubble but the light won’t typically come back on right away. If it’s still off after 50-100 miles you should be good.

I had same issues on my LJ. Swapped O2 sensors, celebrated. Would come back on a few days later.

Ended up doing cat replacement and light has been off since. Hopefully you don’t have to do that!

Yep. Wasn’t fun to pay for or install. Hopefully you don’t have that issue