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Old 11-06-2011, 07:04 PM   #1
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No cat

The p.o. Hollowed out the cat. I noticed it when replacing muffler. The smell from my exhaust is horrible. Is this why. Does this also affect performance?

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Old 11-06-2011, 07:08 PM   #2
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I would just take the cat out if you don't have to get a smog check. Or you can buy a magnaflow cat for $60 from jc Whitney.

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Old 11-06-2011, 07:08 PM   #3
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What engine? May not pass emissions now. If fuel injected it will throw check engine light unless oxygen sensors are tricked into believing its there.
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Old 11-06-2011, 07:38 PM   #4
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What engine? May not pass emissions now. If fuel injected it will throw check engine light unless oxygen sensors are tricked into believing its there.
Not worried about emissions test. Have friends in good places. I was just wondering about performance, gas mileage,and why it smells so noxious.
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Old 11-06-2011, 07:41 PM   #5
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Oh, I know we aren't talking about committing a Federal crime in here....
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Old 11-06-2011, 09:19 PM   #6
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Performance wise you should gain a bit of hp and tq but im not to sure about gas mileage.
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Old 11-06-2011, 11:31 PM   #7
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There's no sensor on the cat. And the smell is from the old cat. It will in fact run much better without one.
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Old 11-07-2011, 07:15 PM   #8
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Thanks for the help guys. I think I'm going to get one in the spring
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Old 11-07-2011, 08:44 PM   #9
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Backpressure from a working cat is so minor there's barely a difference in power whether it's there or not, on a stock or near stock engine. And it has no effect on fuel economy. If it was bad and clogged then it's another story. Or if it was a really built up engine that needs to breathe that much. I had to gut mine when the substrate broke down and started rattling around inside. On my '93 there's no downstream 02 sensor so no codes, not sure about 94-95. I replaced it when I did the rest of the exhaust. Hollowed out it's basically a resonator chamber and makes an annoying tinny noise, and what you're smelling is unburned fuel that normally gets cooked in the cat.
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Old 11-08-2011, 12:08 PM   #10
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What engine? May not pass emissions now. If fuel injected it will throw check engine light unless oxygen sensors are tricked into believing its there.
YJ's are all OBDI and have no secondary 02 sensors so you can gut at will. There is no performance benefit to having a cat, but it does get rid of the noxious fumes. Comes in handy especially if you like to do slow trail stuff or hit drive thru's frequently.

If you do get a replacement, make sure it has a heat shield.
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Old 11-08-2011, 03:06 PM   #11
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So I bought a 1993 Wrangler YJ in incredible condition (no rust, 53K original miles) last week for taking up when I go hiking. Too good to be true? Well sort of. The condition is great and miles are actual (checked the CARFAX), but somebody had either taken off, or stolen the Catalytic Converter and placed a direct pipe to muffler and it, needless to say did not pass emmisions. I have a couple of questions:

1. Since a thief probably cut the pipes on either side of the CAT, is it best just to replace with Crown exhaust kit from Manifold to tailpipe (found it for $399, and somone to install for $100), or is it better just to weld a CAT on the existing pipes (which is around $200+ anyways)?

2. I thought the Jeep was a little noisy when I bought it, but figured that must be what old jeeps sounded like and could not pass up a jeep with these miles on it. I am wondering if anybody has done an exhaust kit replacement and if it made their jeep sound/run noticeably quieter (keep in mind I have a loose pipe on both sides connecting the muffler to the other pipe that feeds manifold)?
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Old 11-08-2011, 04:25 PM   #12
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JG....personally I would take a look at the rest of the exhaust system and see what the overall condition of your currently installed system looks like. If some of your pipes are showing corrosion or signs of muffler mender applied to it, you will be better off going with an entire stainless system to keep from nickle and diming yourself along the way.

If the rest of the system looked like it was in good condition, a quick cat and weld would make more sense.

If you go the route of the kit, you should really give it a shot and try to install it yourself. An exhaust kit is one of the easier installs to do and personally feel that $100 for an install is an unreasonable price. A creeper and can of PB Blaster with a wrench or two will be followed by a sense of accomplishment

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