What are the chances that the heat shield right above it is the problem?

 

none, the muffler shop confirmed that it was my cat.

 

you will fail smog, if you have to get it checked. Its also a federal violation. They sell these things called mil eliminators to get rid of the check engine light when you remove the rear o2 sensor. the rear o2 is really only to make sure the cat is working for emissions. Lots of people with no smog will just cut them off, especially if they go bad. You might even be able to sell them in a non working condition for $100 due to all the platinum in them. That is also why most junk yards will not have any (because they recycled them for $$) I'd suspect that new ones would be $400+.

 

You can cut the pipe and run a straight pipe with an O2 sensor adapter in between where the cat was but its illegal for street use, which if your just offraoding isnt a problem. All it is is a threaded collar welded into a hole cut into the exhaust so the sensor can be threaded in an read the level of carbon output. Here are a few you can look at:
http://www.google.com/products?q=o2...=UTF-8&ei=JMJCSta5GoO2swP2-6jMDw&sa=X&oi=product_result_group&resnum=4&ct=title

Ive known a couple of hotrodders who do that with a pice of straight pipe with 3 bolt flange connectors on either end and weld the same size connectors to their cat so they can swap in and out for track or road. As far as any vehcile emissions laws, permenant removal of a catalytic is against the law in all fifty states for street legel vehicles that came factory equipped with one.

 

Hey, first post here... been lurking for a bit though.

I actually did this last week. I was on a road trip from California to Missouri last week and after filling up at a gas station in Utah, I pulled away and my Jeep was very underpowered and was making a noise of what sounded like an exhaust leak. I could only do 60mph on the flat road with the gas floored in 5th gear.

To make a long story short, I pulled into a mechanic and he confirmed it was the cat. He took a saws-all to the exhaust on both sides of the cat and sure enough there was a big chunk of my cat stuck sideways in the pipe between the housing and the muffler. That is what caused the restricted power.

He hooked me up with a straight pipe after taking out the cat and housing. Jeep runs just fine, in fact, it was more power now. Now that I made it to MO with no problems, I'm going to get a cat put back on this week.

As a previous posted said, it's illegal to run a car with no cat and your vehicle can be impounded.

To answer your question directly: No, it shouldn't affect any sensors. Jeep should run fine.

 

you can get a highflow magnaflow cat for about $110 from 4wheeldrive parts. it includes the downpipe and is all stainless. very good deal. bolts right on in place of the old stuff. stay legal.

 

x2. its not just about staying legal, you need the cat(s) for backpressure to keep the low end torque. remove the cat and you will lose power.

 

just cut it out and gut it and put it back in.

 

I did this with my 98 sport...No check engine light and better sound.. :thumbsup:

 

A local muffler shop here put a new cat on mine for like 175. Its probably aftermarket. It does fine.

 

You guys have to remember that those were completely different engines that were with completely different engineering. Back in the day when cats started becoming mandatory, auto engineers just slapped them into the exhaust system, not doing anything with the engine to work with it. Now days, they have the engines engineered to run better with the cat by having the rest of the system with very low restriction. Aftermarket exhaust systems don't do anything for modern cars anymore except inflate the owners ego

 

Your cat isn't reducing power. The exhaust is engineered to breathe out as much as is inhaled through the intake. Performance cats are needed for when you are increasing intake flow. A free flowing cat won't increase what comes in since that is already a fixed amount. The front O2's are what gives you your base air fuel ratio. The rear O2 is what determines how well the front O2's are doing. Without the cat the system won;t have an accurate diea on how much oxygen is actually in the exhaust. This can result in decreased fuel economy and should cause a catalyst efficiency DTC. Obviously you are tampering with federal emmision laws and will fail e-check too if it's required in your area. In my opinion vehicles that are fuel injected run better and more efficient with the cat installed and in proper working condition.

-Dana

 

I removed the cat from my 93xj and lost power and mpg as a result. Sounded a lot faster though.

 

Haven't we already had this argument in the last week? :brickwall:

 

yea, recurring theme huh? even tho there is a FAQ on How Cat(s) work.

 

cut you cat off, and gut the cat..that way you still have a place to plug your 02 sensor in....i did that, and i havent noticed any change in power or mpg ...and my check engine didnt come on

 

Just cut it off.When you get it out put a piece of pipe in it place.Drill a hole where the 02 was, Get a 18mm nut to put the 02 back in,No CEL.I have done this many times.It will not affect anything but sound. You won't loose backpressure, I have also passed a smog test like this. If they do see it, All you have to say is it came that way. Good Luck

 

Go to a muffler shop and pay the man. I took mine to a shop two weekends ago (note: don't let your wife splash your Jeep through ocean surf... when cold ocean water meets hot cat, the cat will contract, cracking the cover and busting up the insides).

Mine needed to be welded in, or I would have done it myself. When they showed me the quote (little over $200), I pointed to their Magnaflow banner and asked if I could get a high-flow one thrown in instead. $280 total for parts and labor, and I was out the door in under an hour.

Performance is a little better, but it sounds great. Anything is better than the angry wasp noise.

 

the rear 02 sensor does not have anything to do with the fuel, the second 02 sesnor only determines whether the cat is good or not...cut it off and gut it and put it back on...who cares about emissions...sure our kids wont be able to see polar bears in the future, but i never got to see dinosaurs and u dont see me complaining...but then again if your state has emmison controls and checks your car, then i would get a new cat ...but here in SC there is no such thing

 

the rear 02 sensor does not have anything to do with the fuel, the second 02 sesnor only determines whether the cat is good or not...

So the factory service manual is wrong?

Do you have some some info that helps prove this?

The cat is gutted on my '98. I get horrible MPG.

 

The downstream O2 does affect the air fuel ratio. It's like a final check to tell if the PCM calculation based on upstream readings is correct. The two work together to make the air/fuel ratio as efficient as possible. It also checks to see if the cat works, but that isn't it's only purpose.

-Dana

 

I can only tell you what i have experienced as i have done this on more than one jeep. Sound is the only difference. My DD 4 cyl 5speed gets between 17 and 20 on the highway depending on the wind. In town i get mixed because i wind it up to 3k or better before i shift. Its been the same for many, many miles now. But sounds more like a ricer because of it. My trail jeep still has it on there, No reason to take it off unless its bad. I could care less about sound anymore, I just dont see why i should spend more than $25 dollars to fix the problem when it occurs. Its now gaining me anything, But its not taking anything away either. If its bad, Try it for yourself, Its not like your throwing a good cat away, Then you will know first hand.

 

My cat is rattling really bad and I was just going to cut it off but then i realized that there is an O2 sensor connected to it. Is there any way to replace it with something that I can hook the O2 sensor into?

I have a 1997 TJ with the 2.5L engine and the cat was just replaced by the dealer under emissions recall E-22. Parts and labor were free. You might want to check w/your local dealer to see if your cat has been subject to a similar recall.

 

Interesting

http://www.jeepforum.com/forum/showthread.php?t=312129

 

darrel c... 2003-2006 have a pair of mini cats just off the manifold... thats where the O2 sensors are on our jeeps. the 3rd 'big' cat is for more emissions. i cut mine off last year when i did my long arm kit and ran straight pipe to a magnaflow muffler...out the back.. increased perfomance sound and no codes.

 

Thanks for the reply...

 

i got this magnaflow cat-back system,do i cut my catalytic converter and muffler off put this in and curve it out before the rear passanger tire? or do i cut just the muffler off and have this come out right where my e brake line happens to be?

 

can i take off my catalytic converter to my jeep wrangler 2004 with out probleme

 

That depends on what state you live in. You didn't fill out your Profile which would have included that information, please complete it. If you live in a state that inspects the smog system, like California does, you'd have to reinstall it.

Don't remove it for performance reasons, you won't notice any improvement afterwards.

And a big welcome to JF!

 

i did not remove the catalytic converter on my wrangler, but i let a guy talk me into selling it to him and he kept it for 2 years. HE removed it. He found out he wanted an automatic after a couple of years and i bought it back.

it's a 98 sahara 5 speed 4.0 and from what i remember (and i had driven it for 12 years) from before, fuel consumption is way higher and the check engine light is on. otherwise i don't see much difference.

he let it get run down in the two years he had it and i've been restoring it to what it was when i sold it, as funds become available. the CAT and new plugs are on the "to-do" list. that may help consumption.

i drive it mostly on the farm right now, with a few trips to town once in a while and there's a little country store nearby that sells unleaded fuel with NO alcohol, that i've been using in it. it is higher octane and i don't hear the pinging the 87 octane alcohol blend causes.