Bad Cat Converter -
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post #1 of 8 Old 01-19-2011, 02:17 PM Thread Starter
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1993 XJ Cherokee 
Join Date: Aug 2009
Location: Melbourne, FL
Posts: 9
Bad Cat Converter

Alright so here is the problem, whenever I start my 1994 XJ, it sounds like a bunch of rocks rolling around. The sounds goes away as I push down on the gas but comes back as soon as I let off. It also fades away as the Jeep gets hotter. Typically this is a bad converter, right?
If it is bad, can I take it off, until I get the new one? Will it sound/smell really bad? I understand it is illegal, and I don't live in CA so I don't have to pass emission tests.
I was thinking about getting a MAGNAFLOW Direct Fit converter. Any options/better options are greatly appreciated.

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post #2 of 8 Old 01-19-2011, 02:47 PM
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2000 XJ Cherokee 
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Gently tap on the converter with a plastic hammer and see if anything sounds loose inside. You could have bad motor mounts, a bad transmission mount, or just need some new exhaust hangers.


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post #3 of 8 Old 01-19-2011, 03:07 PM Thread Starter
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1993 XJ Cherokee 
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Location: Melbourne, FL
Posts: 9
Yep, definitely the cat. The motor mounts were replaced with some beefy new ones about 50K miles ago. When I pull anything on the exhaust it is all solid. As for the transmission mounts, I don't know. But I do the when I tapped the cat a few times, it sounded like rocks. The Jeep has 'bout 220K on it, and the cat hasn't been changed that I know of.
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post #4 of 8 Old 01-19-2011, 03:34 PM
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I know it's bad form to suggest taking the cat out of the exhaust system and I'm not suggesting you do it, but it just reminds me of a conversation I had a couple days ago.

I was talking to my brother in law (sister's husband, big car guy), about needing to replace mine since it was getting the rocky type sound. He said, "Oh hell, I just take mine off and run a piece of pipe up in there and knock all the crap out and put it back on." Told this to my other brother in law (wife's brother this time, who is a factory line mechanic) and he said "Yeah, that's what all the guys at the shop do to theirs."

I had no idea it was so prevalent.

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post #5 of 8 Old 01-19-2011, 05:33 PM
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1994 XJ Cherokee 
Join Date: Jul 2005
Location: Fairfield, Maine
Posts: 4,253
A new CAT really isn't THAT expensive. I would take care of it, either way, sooner rather than later. When the broken up catalyst finally plugs the outlet the Jeep will run very poorly, if at all. Usually this will happen on a long camping trip with the family while towing a pop-up camper trailer down I-95.


'94 Cherokee Country
Engine: 4.0 HO, Sealed canister filter, 3 core CSF steel radiator, CatCo cat, Dynomax Turbo Flow muffler.
Electronics: Remote start/locks, Pioneer DEH-P7800MP w/XM, Polk Audio speakers, Garmin Nuvi 660 GPS, Cobra 148 GTL P&T w/Wilson 1000.
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Tires/Wheels: 33x10.5x15 BFG Mud Terrains on Alcoas.
Misc: Garvin Wilderness rack, Safari Snorkel, Redline Tuning hood lifts.
Awaiting installation: Autometer A pillar gauge pod, oil, water, & tranny temp guages, PIAA driving lights, Goferit tie-rod flip bushing, '95 Brake booster and M/C, M.O.R.E. Motor mounts, TnT Custom 1.5" Shackle.
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post #6 of 8 Old 01-19-2011, 05:51 PM
It's the crank sensor!
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1999 XJ Cherokee 
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Location: Central Minnesota
Posts: 8,850
Pop a new cat on there. If cost is an issue, you can source them for under a hundred bucks..............

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post #7 of 8 Old 01-19-2011, 06:30 PM
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1990 XJ Cherokee 
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Location: San Diego, CA
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x2, just replace it. since you dont live in CA, you can get them very cheap. CA legal cats go for around $120+...

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post #8 of 8 Old 01-19-2011, 08:05 PM Thread Starter
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1993 XJ Cherokee 
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Location: Melbourne, FL
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Thanks guys. I'm getting a new one for sure, I was just talking temporarily removing it, for like two..ish weeks.
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