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Unread 06-29-2013, 01:30 PM   #16
C2tuck
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Ok...I lied. The check engine light comes on at start-up. And then goes off. So there doesn't seem to be a code unless there is one stored.

I pulled off the air cleaner and the throttle body was NASTY! Cleaned it up the best I could without taking it off right now. I revved it up and it has a pretty bad hesitation on the throttle response. I think it's actually backfiring from both the tailpipe AND the throttle body. I wouldn't mind doing a full exhaust as long as it will convert over to the I6 when I finally swap it over. I'm sure the cat is trashed.

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Unread 06-29-2013, 03:14 PM   #17
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Originally Posted by C2tuck View Post
Ok...I lied. The check engine light comes on at start-up. And then goes off. So there doesn't seem to be a code unless there is one stored.

I pulled off the air cleaner and the throttle body was NASTY! Cleaned it up the best I could without taking it off right now. I revved it up and it has a pretty bad hesitation on the throttle response. I think it's actually backfiring from both the tailpipe AND the throttle body. I wouldn't mind doing a full exhaust as long as it will convert over to the I6 when I finally swap it over. I'm sure the cat is trashed.
Pull the codes if any are stored. Ignore 12, 33 (espically if you do not AC), 55.

Run it after you clean the crap out of the TB with carb cleaner while you have it running. How does it run now once it is warmed up? Still running crappy?

If you want to determine if the cat converter or muffler is the problem, cut the exhaust after the O2 sensor but before the cat/muffler somewhere on a straight section like where it crosses over from the drivers side to the passengers side behind the base pan If it runs good now the cat and/or muffler is NG. If nothing changes it probably not the cat or muffler. You can fix it with a 2" OD x 2" ID adapter and two muffler clamps if you have no welder.

Bottom line is it gets real expensive throwing parts at an unknown problem.

If there is anything 'off' with any part off the emissions system you should get a lit CEL telling you that a DTC has been set. That is the first thing you need to find out.

If any problem exists after the emissions sensors, the O2 being the last one then no DTC gets set and no CEL lights up.

Then you can safely assume that if the fuel is good and you have decent compression the cat is clogged.
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Unread 06-29-2013, 05:41 PM   #18
C2tuck
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Would that cause the backfiring through both the throttle body and the exhaust pipe?
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Unread 06-29-2013, 06:27 PM   #19
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Would that cause the backfiring through both the throttle body and the exhaust pipe?
Timing

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Unread 06-30-2013, 12:59 AM   #20
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Ok. So the wife went out with the girls, and the kids wanted to go to the movies and wanted to take the jeep. The movies are about 20 miles away so we took off. She ran fine until about half way there and then started hesitating while at highway speeds. After the movie on the way home, it started running horrible after about 5 miles. It literally sounded like popcorn popping under the hood with absolutely no power at all. Going up small hills on the highway I think I was doing 30-35 mph.

If it was timing it would run bad way before 5-10 miles on the highway right? Also looking into setting the timing on the forum, everyone is saying that it is computer controlled and that advancing the dist won't do any good...so,if it IS the timing...how do I set it??
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Unread 06-30-2013, 01:10 AM   #21
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change the god dammmm cat!

i'll put $10 in your membership account if it's not the problem!
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Unread 06-30-2013, 06:35 AM   #22
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change the god dammmm cat!

i'll put $10 in your membership account if it's not the problem!
At this point I'm inclined to agree with mike_breaker_5, especially since it took less time to stumble coming back since the cat was already hot from the trip to the movies......but I ain't bettin' no stinkin' 10 bucks!
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Unread 06-30-2013, 05:20 PM   #23
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Timing

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X2 check your timing to see it the timing chain is shot.

A easy check is to place a timing light on her and see if the mark jumps. If so timing chain.
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Unread 06-30-2013, 05:50 PM   #24
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if it was timing it would be running terrible all the time. he said it ran fine for a short time in b/n fits.
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Unread 06-30-2013, 07:59 PM   #25
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if it was timing it would be running terrible all the time. he said it ran fine for a short time in b/n fits.
No it would not neccasarily. The chain can stretch more once it heats up. I would check the timing. Back fires are caused by a timing issue or raw fuel being dumped into the cat from a cylinder not firing. He said its backfiring through the throttle body and exhaust. Sounds like timing it's firing to soon and then dumping off the fuel that's left into the exhaust. Timing is the only explanation I see that would cause both his symptoms.

ECM sets ignition timing. Mechanical time is still set by the chain and sprockets.

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Unread 06-30-2013, 08:24 PM   #26
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Ok. Thanks for all the reply's. I'll check the timing tomorrow after work. I'm also gonna call and get a price on a full exhaust system. Anyone have any recommendations?? Does both the 4 and 6 have the same exhaust as I am going to swap??

Thanks again guys. And even tho she isn't running right...she's still fun as hell to drive!
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Unread 07-01-2013, 06:01 AM   #27
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Ok. Thanks for all the reply's. I'll check the timing tomorrow after work. I'm also gonna call and get a price on a full exhaust system. Anyone have any recommendations?? Does both the 4 and 6 have the same exhaust as I am going to swap??

Thanks again guys. And even tho she isn't running right...she's still fun as hell to drive!
The exhaust systems are different. For a temporary test only because defeating a cat converter hurts not helps you, get the exhaust system apart and punch a large hole through matrix of the cat converter. Stick it back together with a muffler pipe adapter and the run it.

If it doesn't bog on you once it is warmed up you probably have a bad cat converter. Replace the exhaust system once you do the engine swap.

Warning: Those loose pieces of matrix in the cat you created can bounce around and get stuck in the outlet of the cat converter shutting you down permanently.
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Unread 07-01-2013, 12:38 PM   #28
C2tuck
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Exhaust is only 300-350 bucks from manifold back at a reputable shop in my town so I'm go an go ahead and replace it. He said that he'd run it 2.5" so that when I swap the motor most of it will still work. Said he'd have to redo from the manifold/header (haven't decided yet) to the converter once the swap is done...so no biggie there. Still gonna throw the timing light on it tonight and see what I can find out. At this point, hopefully it's just the cat!
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Unread 07-01-2013, 01:59 PM   #29
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The exhaust systems are different. For a temporary test only because defeating a cat converter hurts not helps you, get the exhaust system apart and punch a large hole through matrix of the cat converter. Stick it back together with a muffler pipe adapter and the run it.

If it doesn't bog on you once it is warmed up you probably have a bad cat converter. Replace the exhaust system once you do the engine swap.

Warning: Those loose pieces of matrix in the cat you created can bounce around and get stuck in the outlet of the cat converter shutting you down permanently.
Thanks LB for keeping on top of this thread. Kinda funny to see lots of help jumping the gun even though the advice may be accurate before the simple and free stuff is first check off the list. To the OP, yeah, sounds like clogged cat, but try this.... once it starts acting up... shut her down and wait a spell to allow exhaust pressures to normalize. Don't wait so long as for the engine to cool off. Does it run good again? If so, then most likely a clogged cat. Any rattling noise when it is struck with a dead blow hammer? Rattle noise is an indication of the catalyst self destructing. Which case make sure you get a 3-way cat and then also replace your O2 sensor and make absolutely sure you do not have a leak in your exhaust system above the O2 sensor, otherwise any money spent on a new cat will soon be pissed away.
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Unread 07-01-2013, 03:40 PM   #30
C2tuck
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Yes. It does exactly that. It's also worse going up hill or any slight grade. Had to stop 3-4 times the other day just to get home. I'll smack it when I get home and see. Like I said. I'm sure it's trashed.

Hopefully I'll get a little more power once it's fixed cause this thing is a dog! I had a friend that had a TJ with a 4 banger and I don't remember it being this bad.

Again, thanks for all the help guys!
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