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Unread 01-19-2011, 02:17 PM   #1
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1994 XJ Cherokee 
Join Date: Aug 2009
Location: Melbourne, FL
Posts: 6
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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Unread 01-19-2011, 02:47 PM   #2
Real Jeeps have dents.
CJ7-Tim's Avatar
2000 XJ Cherokee 
Join Date: Apr 2002
Location: out in the garage - Minneapolis, Minnesota
Posts: 21,627
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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Unread 01-19-2011, 03:07 PM   #3
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1994 XJ Cherokee 
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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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Unread 01-19-2011, 03:34 PM   #4
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2007 WK 
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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.
2007 WK Overland
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Unread 01-19-2011, 05:33 PM   #5
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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.
Suspension: Old Man Emu 3" lift+OME AAL, JKS adjustable trackbar, QDs, LCAs UCAs, A.C.O.S., DPG Offroad adjustable bumpstop plate, Daystar poly bumpstops.
Steering: Currie HD steering, C-ROK steering box reinforcement, OME stabilizer.
Armor/Recovery: T&T Custom belly skid, Mopar gas tank skid, JKS LCA mini skids, Rock Lizard Super Skink Sliders, Mopar 2" receiver, ARB Bull Bar/Ramsey REP 8.5 winch.
Drive train: D30 front axle w/Superior Chromo D30 axles & outter seals, D/S 4.56 R&P, ARB locker, Ruff Stuff cover. Ford 8.8 rear axle w/Superior Super 88 kit, Ford Motor Sports 4.56 R&P, ARB locker, SOLID cover, Russell stainless lines. Front and rear Tom Woods HD drive shafts, 242 x-fer case w/Tom Woods SYE.
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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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Unread 01-19-2011, 05:51 PM   #6
It's the crank sensor!
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1999 XJ Cherokee 
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Location: Central Minnesota, MN
Posts: 8,429
Pop a new cat on there. If cost is an issue, you can source them for under a hundred bucks..............
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Past Jeeps: 49 Willys, 81 Scrambler, 88 Comanche
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Unread 01-19-2011, 06:30 PM   #7
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1990 XJ Cherokee 
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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+...
Completely stock, and keeping it that way...

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Unread 01-19-2011, 08:05 PM   #8
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1994 XJ Cherokee 
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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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