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Old 08-28-2010, 08:33 PM   #1
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diagnose prob with cat

Whats the best way to see if my cat is getting clogged or if i need to start thinking about servicing it? Ive heard knocking on it with a mallet and listening for rattle I havent tried it yet.

also while on this note, how can I tell if my fuel filter needs to be replaced and if my fuel pump needs servicing

I have:

95 YJ 4.0L
109XXX miles

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Old 08-28-2010, 10:22 PM   #2
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Like you said , Tapping on the cat is the quickest way to check the cat.
as far as the fuel filter goes, if it has been ahwile since you last changed it then it never hurts to change it. I actually change mine every 3rd oil change.
I've never serviced a fuel pump other than changing the filter sock if that is what you meant.
I usually wait to see if the fuel filter corrects any bogging in throttle before going into the tank. To be honest I always went ahead and changed the complete fuel pump, lol cause with my luck I would change the filter sock then the dern thing would go out and have to drop the tank again...maybe someone whos done it more will chime in..

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Old 08-28-2010, 10:27 PM   #3
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whats a good aftermarket replacement for the cat?
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Old 08-28-2010, 11:09 PM   #4
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All of got on this one wasomma, is just go ahead and change out the fuel filter. It's not expensive and it's an easy one man job to do.

When you get the filter off, shake out any internal gas, put it to your mouth and try to blow through it hard. A good filter will let air pass right through with little resistance. If it's difficult to blow through, the filter is full of crud.
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Old 08-30-2010, 10:31 AM   #5
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so i was driving on the highway around 65mph, started to go up an incline and noticed severe power loss in 4th gear and started to slow to 50mph and saw the tach wasnt going over 2000rpms nearly floored.

The check engine light came on and I saw the engine was running 200 to 210 which is warmer than she usually runs by quite a bit.

I parked at work turned it on and listened to the jeep when I revved the engine. There is a strange whistling sound coming from somewhere in exhaust system. The exhaust also sounds weird or at least different. I banged the cat with a funnel and heard a very distinct rattling sound. I'm not sure if its the cat gone bad or if its the heat shield knocking around in there.

I changed the dist cap and rotor recently, however the jeep was running fine for 2 days until this popped up so I don't think that is the culprit. It idles fine, speeds from 0-45mph seem to be ok power and acceleration wise. It's when I get into 50mph+ i see significant power loss in 4th and especially 5th. I wonder if its just a bad cat, and if so I want to see if I can just push the stuff through the cat out and make it straight flowing.

I've never serviced a cat before so I dont know if it is welded on or not. I also have the jeep registered in NE where there are no emission laws so I'm not concerned about passing emissions. I pulled the codes off and I think i got 12 33 51 55, I say think because i only had a couple hours of sleep and blinking red lights seemed to meld together so I'm going to double check those #s later.
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Old 08-30-2010, 10:34 AM   #6
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Same as here, I'd delete it
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Old 08-30-2010, 10:38 AM   #7
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Same as here, I'd delete it
I'd love to, do you know if there are any gaskets or brackets I need to purchase beforehand if I delete. Also would there be any welding involved?

I have a 95YJ 4.0L 5 speed
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Old 08-30-2010, 10:40 AM   #8
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Well I just cut it off and weld in a new piece of pipe...or you can take it off and knock all the crap out of it and put it back on. As far as gaskets go, I couldn't tell ya.
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Old 08-30-2010, 10:44 AM   #9
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Well I just cut it off and weld in a new piece of pipe...or you can take it off and knock all the crap out of it and put it back on. As far as gaskets go, I couldn't tell ya.
My problem is I dont know how to weld which is a shame because the auto hobby shop on base has lifts (which i use) and all the fab equipment you could ever use for free.

Ill just take it off and bang all the crap out and put it back. Is there a way to take it off without removing the stock skid plate?
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Old 08-30-2010, 10:47 AM   #10
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Does someone there with you know how to weld? Its not that hard honestly, the hardest part is knowing what to look at through the helmet.

I'd think you could get it off without taking the SP off, but its all gonna depend if the PO had exhaust put on it and its location was changed.
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Old 08-30-2010, 10:51 AM   #11
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Does someone there with you know how to weld? Its not that hard honestly, the hardest part is knowing what to look at through the helmet.

I'd think you could get it off without taking the SP off, but its all gonna depend if the PO had exhaust put on it and its location was changed.
Naw I got under there (with my dress blues on which was a b#$%^) and I'm sure everything on the jeep is stock. I assume there is going to be play when I disconnect the cat.

Now whats the story with the muffler, is a clogged cat going to do bad things to the muffler or should I mess with it as well.

I might have a bud who can weld, but I dont have a pipe to go in its place
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Old 08-30-2010, 10:55 AM   #12
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It very well could have put some crap in it. I think after you get the cat off you could tilt the muffler down and tap on it and if there is anything in there it should come out. I remember when I was a kid we were going 4 wheeler riding and the truck we were driving had a cat problem. Everything inside broke loose, blew through the muffler, and got stuck in the exhaust pipe (gm used to use wire mesh in the tailpipes in the 70's). Dad had to get out and ram the tire tool in the pipe so he could get all the catylist crap out of it. After that the truck ran alot better and got better mpg
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Old 08-30-2010, 10:58 AM   #13
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Oh and also whats the word on the 02 sensor. Is it before or after the cat? if it is after the cat will I encounter any issues running with a cleaned out cat
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Old 08-30-2010, 10:59 AM   #14
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It very well could have put some crap in it. I think after you get the cat off you could tilt the muffler down and tap on it and if there is anything in there it should come out. I remember when I was a kid we were going 4 wheeler riding and the truck we were driving had a cat problem. Everything inside broke loose, blew through the muffler, and got stuck in the exhaust pipe (gm used to use wire mesh in the tailpipes in the 70's). Dad had to get out and ram the tire tool in the pipe so he could get all the catylist crap out of it. After that the truck ran alot better and got better mpg
Yea I'm looking forward to the increased HP, I hate cats
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Old 08-30-2010, 11:00 AM   #15
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The o2 sensor should be before the cat
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Old 08-30-2010, 11:03 AM   #16
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The o2 sensor should be before the cat
awesome, thanks for all the great info man i appreciate it
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Old 08-30-2010, 11:05 AM   #17
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You betcha!
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Old 08-30-2010, 04:06 PM   #18
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anyone else know if there is any welding/cutting needed to remove a stock cat? i just looked at it and it seems like there isnt going to be any needed but Id rather know in advance than when I have it up on the lift
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Old 08-31-2010, 05:39 PM   #19
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So i cut up my exhaust system today and sure enough the cat had blown through and everything was a mess in there. So what I did was cut the muffler off cuz that thing is toast from all the debris from the cat and disconnected the pipe at the header and cleaned the whole system out including the cat. Replaced the pipe and cat and left it running open from there and damn does the jeep sound good. Ill post a pic of the torpedo i found in the pipe.

I'm looking at new kat-back systems, anyone have a good suggestion currently this one is my first choice however I dont know how I feel about the polished steel tip.

Exhaust System, Tfx Kat-Back 4/6 Cyl*PST-862872 by the Jeep Specialists | Morris 4x4 Center
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Old 08-31-2010, 05:50 PM   #20
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That may or may not affect performance

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Old 08-31-2010, 06:19 PM   #21
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Old 08-31-2010, 07:22 PM   #22
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Old 08-31-2010, 08:23 PM   #23
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