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Unread 07-08-2002, 07:38 AM   #1
Mels95YJ
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Question about cat

Ok guys, I need some help here. Last year, my cat went out, and I had it replaced by the dealer. It was still under warranty, so I got a brand-spankin' new one. The cost would've been $800. Anyways, it's started making that typical "beans in a can" noise again, and it's getting worse. I haven't crawled underneath yet to see if a weld has broken loose on the pipe somewhere, but it has got me concerned. I mean, it's still under warranty, but I need to figure out what would cause 2 cats to go out within a year's time. Any suggestions? I was told on another forum that putting a 180* thermostat in it could cause problems since it's not getting hot enough to burn off all the fuel. The thing is, when the first cat went out, it had the factory 195* thermo in it. So, I'm all ears for any suggestions. Thanks in advance.

Mel

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Unread 07-08-2002, 09:53 AM   #2
johny1i
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Do you spend much time offroad? A couple of good hits to the converter will break that honeycomb into pieces inside. Otherwise, an overly rich mixture (unburned gas) going into the converter will make it too hot and cause the honeycomb to get brittle and break up. Check your sparkplugs, and if they aren't too sooty or otherwise indicating a rich mixture, then that probably isn't the culprit. An overly rich mixture will also produce that "rotten egg" smell, so if you aren't smelling that then your engine is probably running lean enough and you can rule that possibility out.
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Unread 07-08-2002, 09:55 AM   #3
ssg11bravo30
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A 180 degree thermastat will do damage as the onboard computer will think the engine is not warmed up and continue to run rich. This will damage the cat but it shouldn't cause it to make the rattle. Is the heats shield secure? Has the cat been smacked? This could cause the internals to break free and bounce around but it would have been a pretty good impact/dent. If the dealer just replaced it I would take it back and have them tell you what is wrong- is it still under the emissions warranty?
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Unread 07-08-2002, 11:33 AM   #4
Mels95YJ
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It is still under the emissions warranty. It hasn't been offroad since I'm still looking for people to wheel with. I haven't had a chance to see if any welds have come loose yet. It rattles when I let off the gas and let the engine do the braking (coming to a red light, etc). It's not rattling as bad as it was right before I replaced it before, but over the last couple of weeks, it has gotten a good deal louder and frequent.

I sometimes smell gas fumes, but that could just be from having the bikini combo on. I plan on putting a 195* back in it when I do another oil change in probably a month. I recently changed the spark plugs and gapped them at 35. It may just be something has come loose and causing the rattle, but I just like to have an idea of what could be causing the damage if there is damage. I can understand having 1 cat go bad, but having another go bad this close together has gotten me worried. Thanks for the help and suggestions already.

Mel
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Unread 07-08-2002, 07:15 PM   #5
Jeepchik
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I had my cat break on my 95 yj and more recently on my 97 tj. Both of them happened when I almost ran out of gas.
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Unread 07-08-2002, 07:34 PM   #6
Mels95YJ
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Ok, I crawled underneath the Jeep to take a look. Here's the question. How much play should there be in the muffler/exhaust. You can grab the muffler and move it back and forth approximately 1/2" to 3/4". I mean the muffler all the way back to the tip. Could this be what's rattling? Like I said earlier, it rattles the most when I'm letting the engine slow me down. If I press in the clutch or put it in neutral, it doesn't do it. Any thoughts???

Mel
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Unread 07-08-2002, 09:22 PM   #7
johny1i
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Only if it's hitting something (like the skidplate) when it moves. Double check the nuts that hold the front pipe to the exhaust manifold. If they've worked loose, it can allow the whole exhaust system to sway. Also check the rubber hangers near the end of the system to make sure that they haven't torn or anything.
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Unread 07-18-2002, 01:17 PM   #8
Mels95YJ
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Update:

Well, I took it to the dealer today, and sure enough, the cat has gone bad. It's only been 8 months!!! Luckily it's still under warranty, so it's free on my part. They also hooked it up to the computer and nothing else showed wrong with it. So, I guess I just got a bad cat from the factory. Let's hope anyways. I am going to be changing back to a 195* at my next oil change just to be safe. Just thought I'd let ya know the outcome.

Mel
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