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Old 05-20-2011, 05:33 PM   #1
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3 cats in my exhaust!?

I have 3 catalytic converters! Do all TJs have 3?

There are 2 smaller cats right under the exhaust manifold. Each one has a forward and rearward O2 sensor (for a total of 4 O2 sensors). The 2 pipes go into one pipe with a larger cat under the transfer case skid plate. No O2 sensors near this one.

The guy at the dealership said the 3rd cat is for California emissions. The emissions decal under my hood says Federal and California compliant.

Are all TJs California compliant, or just the ones sold in California?
I don't live in California so can I remove the 3rd cat? I'm sure the 2 cats near the engine are protecting the environment just fine.

Thanks for any info!

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Old 05-20-2011, 05:36 PM   #2
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mine only has 1 + a flowmaster, and only 2 O2 sensors, 1 sensor right at the manifold and 1 sensor at the back before the flowmaster

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Old 05-20-2011, 05:37 PM   #3
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Lucky you.

Californication, has much stricter emissions requirements then do the Feds/rest of the US. So if yours is CA/Fed approved, you got the 3 cat special.

Ours is Fed only, 1 cat.

And 2 O2 sensors instead of CA's 4.


Sorry.
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Old 05-20-2011, 05:43 PM   #4
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1 here...
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Old 05-20-2011, 05:44 PM   #5
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The newer tjs have 3 cats, the older ones just one. i think they started that in 01 or something. Just had to replace mine.
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Old 05-20-2011, 05:49 PM   #6
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Quote:
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Californication, has much stricter emissions requirements then do the Feds/rest of the US. So if yours is CA/Fed approved, you got the 3 cat special.

Ours is Fed only, 1 cat.

.
I live in california...1 cat and 2 o2 sensors I believe. I get smogged every couple of years like I need to, and have never had an issue passing. Like someone said, it probably has to do with the year rather than the state he lives in considering mine is a 99.
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Old 05-20-2011, 05:51 PM   #7
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Correct. My 97 came with one cat, California model, later ones got the precats.
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Old 05-20-2011, 05:51 PM   #8
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3 cat's that's just ridiculous, I put a high flow cat by flowmaster in mine.
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Old 05-20-2011, 05:54 PM   #9
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2004 is when they went to 3 cats.
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Old 05-20-2011, 06:01 PM   #10
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2004 is when they went to 3 cats.
...except the OP has a 2001?
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Old 05-20-2011, 06:26 PM   #11
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2004 is when they went to 3 cats.
some 2000's got 3-cats (california emissions versions maybe?), and all 2001-06's had 3 cats...even 4.0L WJ's and XJ's in that range.

also keep in mind two O2 sensors are after the mini-cats off the exhaust manifold, so you can't remove them. actually, by federal law you can't modify any of them.
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Old 05-20-2011, 08:40 PM   #12
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Quote:
Originally Posted by UnlimitedLJ04
some 2000's got 3-cats (california emissions versions maybe?), and all 2001-06's had 3 cats...even 4.0L WJ's and XJ's in that range.

also keep in mind two O2 sensors are after the mini-cats off the exhaust manifold, so you can't remove them. actually, by federal law you can't modify any of them.
What about the 3rd cat, that's not monitored by an 02 is it??
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Old 05-20-2011, 09:05 PM   #13
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I took my LJ to the dealer recently to have the cats replaced under warranty. They subed the work out to a local exhaust shop. The day after I got it back I rolled under it to look. They didn't install the 3rd cat. Jeep runs better than ever. No codes.
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Old 05-20-2011, 09:14 PM   #14
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Originally Posted by rbloodhound
I took my LJ to the dealer recently to have the cats replaced under warranty. They subed the work out to a local exhaust shop. The day after I got it back I rolled under it to look. They didn't install the 3rd cat. Jeep runs better than ever. No codes.
I always wanted to know this. I did ask about removing the "3rd cat" it's not monitored by an 02 right? All I got was a bunch of "wise cracks" about removing the cats and laws, pretty much not to do it. Why can't it just be removed? I mean the two mini cats are not enough?. Both have their own sensor. What the hell is the point of the 3rd (main cat)? somebody please answer this.
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Old 05-20-2011, 09:18 PM   #15
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guys the 3 cats didnt start until 2000 model year when they went distributor less and installed the horse-shoe intake manifold. 97-99 have the log intake/1 cat/distributor ignition. I think some late 99 models may also be like this or all 99 models but 2000+ have 3 cats.
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Old 05-20-2011, 09:46 PM   #16
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I always wanted to know this. I did ask about removing the "3rd cat" it's not monitored by an 02 right? All I got was a bunch of "wise cracks" about removing the cats and laws, pretty much not to do it. Why can't it just be removed? I mean the two mini cats are not enough?. Both have their own sensor. What the hell is the point of the 3rd (main cat)? somebody please answer this.
It can be removed, but as stated you will be breaking a federal law. If you are ok with that, go for it. I know it wouldn't bother me much if I knew that mine was plugged up. I would rod that thing out in a heartbeat. If the 2 pre cats would have been enough, I really doubt Jeep would have spent all the extra money putting a 3'rd one on though
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Old 05-21-2011, 01:14 AM   #17
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ipleadda2nd

you can remove the third cat and nothing should change, but just a bit of fore warning if you ever have it serviced or if you go to sell it, it will be violating federal law because it came from the factory with all three cat's.

i've dealt with this problem on a used 2001 TJ that I was looking at and was going to get, but when I took it in for a DMV and smog inspection the guy told me that they wont and will not check it because it was missing one of the three cat's that was suposed to be on there so to say the least I didn't get that 2001 TJ instead I got my 2000TJ which I love.... Hope this helps abit with your question.

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Old 05-21-2011, 04:59 AM   #18
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Originally Posted by wolfsbone01
ipleadda2nd

you can remove the third cat and nothing should change, but just a bit of fore warning if you ever have it serviced or if you go to sell it, it will be violating federal law because it came from the factory with all three cat's.

i've dealt with this problem on a used 2001 TJ that I was looking at and was going to get, but when I took it in for a DMV and smog inspection the guy told me that they wont and will not check it because it was missing one of the three cat's that was suposed to be on there so to say the least I didn't get that 2001 TJ instead I got my 2000TJ which I love.... Hope this helps abit with your question.

Wolf
Thanks for the response here in CT we don't do a smog test anymore. The vehicle is scanned but with OBDII I believe
if the check engine light is not on we are good. If the main cat is not monitored by an 02 sensor I am pretty sure it will pass here in CT. They stopped doing inspection
here too years back, I don't see an inspector looking underneath saying "wait,
are you supposed to have a 3rd catalytic converter under this thing?" That being said I am not going to rip the thing off, but if it does go bad, I'm not going to pay to replace the thing
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Old 05-21-2011, 05:09 AM   #19
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Yeah mine is a 2002 Wrangler with California Emissions it has 1 O2 sensor for the first 3 cylinders, 1 O2 Sensor for the last 3 cylinders. It then has two pre cats which each have an O2 sensor in the pipe after the pre-cat. Then further down you will find a full size cat, this is the one that won't have a O2 sensor in it.

Now this is an 2002 that was bought new in California, so it may be different than the standard Federal emissions on vehicles sold to the other states.
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Old 05-21-2011, 05:45 AM   #20
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Yeah mine is a 2002 Wrangler with California Emissions it has 1 O2 sensor for the first 3 cylinders, 1 O2 Sensor for the last 3 cylinders. It then has two pre cats which each have an O2 sensor in the pipe after the pre-cat. Then further down you will find a full size cat, this is the one that won't have a O2 sensor in it.

Now this is an 2002 that was bought new in California, so it may be different than the standard Federal emissions on vehicles sold to the other states.
Mine is a 2001, 50 states compliant like most. I can't understand why the main cat is not monitored by the vehicle or a 02 sensor. I'm not complaining, 5 or 6 sensors would suck but if not monitored I don't see the point in replacing it if it goes bad. actually, unless it clogs you really have no idea if it's doing it's job because it does not have an 02 sensor. If a precat goes bad or doesn't convert your emissions, one of the sensors should pick it up and trigger a CEL. so how do you know if the main is not working?
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Old 05-22-2011, 10:48 AM   #21
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Thanks!

Thanks for all the info!

I believe in cats. I think a high quality cat serves a purpose and doesn't affect performance much. But 3, really?
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Old 05-22-2011, 11:25 AM   #22
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Thanks for the response here in CT we don't do a smog test anymore. The vehicle is scanned but with OBDII I believe
if the check engine light is not on we are good. If the main cat is not monitored by an 02 sensor I am pretty sure it will pass here in CT. They stopped doing inspection
here too years back, I don't see an inspector looking underneath saying "wait,
are you supposed to have a 3rd catalytic converter under this thing?" That being said I am not going to rip the thing off, but if it does go bad, I'm not going to pay to replace the thing
You can always gut them and leave them on the vehicle as well. I know 2 different Jeeps (both with the 3 cat set up) that have nothing inside any of the cats and they run just fine with no codes.
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Old 05-22-2011, 11:38 AM   #23
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Originally Posted by Scoob

You can always gut them and leave them on the vehicle as well. I know 2 different Jeeps (both with the 3 cat set up) that have nothing inside any of the cats and they run just fine with no codes.
Need dummy 02 sensors also but I'm not trying to be illegal here lol.

The answer I usually get when asking about removing the [non monitored main cat] is "it's illegal" and "don't do it" . Why 3 cats? The 2 minis are not enough?
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Old 05-22-2011, 11:49 AM   #24
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Need dummy 02 sensors also but I'm not trying to be illegal here lol.

The answer I usually get when asking about removing the [non monitored main cat] is "it's illegal" and "don't do it" . Why 3 cats? The 2 minis are not enough?
No you dont need to do anything to the O2 sensors. The 2 important ones that control air/fuel are before the pre cats.

Only going by what I have been told on the reason for 3 cats. Is that the first 2 pre cats are small to heat up quickly and alone would not pass a sniffer test. And that the "main" cat alone would not pass the sniffer test before it is warmed up. According to the Jeep guy I talked with it needs all three to be legal. If they could have done it with 1 or 2 they would have.
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Old 05-22-2011, 05:44 PM   #25
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No you dont need to do anything to the O2 sensors. The 2 important ones that control air/fuel are before the pre cats.

Only going by what I have been told on the reason for 3 cats. Is that the first 2 pre cats are small to heat up quickly and alone would not pass a sniffer test. And that the "main" cat alone would not pass the sniffer test before it is warmed up. According to the Jeep guy I talked with it needs all three to be legal. If they could have done it with 1 or 2 they would have.
I dunno, it does not make sense. If the precats needed the main cat, the main cat
would be followed by a sensor downstream? ehh who cares, I've been trying to figure this out forever. Tell ya what, when my main cat goes bad I am going to run a straight pipe and report the results. I give up
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Old 05-22-2011, 06:26 PM   #26
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I dunno, it does not make sense.
its got to do with how hot they need to run. the mini-cats run far hotter than the main cat....

every year the emissions requirements get more strict. so for any given year (like 1999 vs 2004), the type of emission equipment needed changes so that more emissions can be reduced....like two conversion vs three way conversion cats...

remember back in the early 2000's, you'd see adds for cars/vehicles that said they meet 2011 emissions standards? the requirements are published by the EPA far in advance so manufacturers can keep up. the next big hurdle is 2018....you'll see a bunch emissions related equipment being added before then...like urea injection on diesels for example.
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Old 05-22-2011, 11:29 PM   #27
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but I'm not trying to be illegal here lol.
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Tell ya what, when my main cat goes bad I am going to run a straight pipe and report the results. I give up
In which case you are trying to be illegal

Like I said, I would have no problem doing that either. But just because you don't see a reason for it to exist doesn't matter. It is illegal to remove it, whether its monitored by the pcm or not.
Your results will be the same as everybody else. Because there is no 02 sensor down stream the engine will have no idea its gone, only the environment will.
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Old 05-22-2011, 11:35 PM   #28
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Good enough for me
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Old 05-22-2011, 11:37 PM   #29
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Good enough for me

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