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Unread 06-27-2013, 07:07 PM   #1
C2tuck
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Backfiring...

Ok, so I've always wanted a wrangler and I finally got one. It's a 93 2.5 5spd. It's not perfect but I always like a project! I already plan on swapping a 4.0 in it and have already bought one. I'm sure ill be asking tons of questions when I get around to doing that

But my post for today is about it running bad. It runs fine until its warmed up and then it starts bogging down and backfiring bad! I'm talking downshifting to 2nd on the highway to get it to move. Never overheated or got close to being hot. I've already changed the plugs, wires, dist cap, rotor, oil and filter, and air filter. It was pretty nasty underwood so I cleaned her up a bit.

Any ideas?

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Unread 06-27-2013, 07:33 PM   #2
idaholtby
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Congrats on your first Jeep and welcome to the forum! First and foremost check for codes to see if any are stored. This info may help to pinpoint your issue.
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Unread 06-27-2013, 08:01 PM   #3
laybackman
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Quote:
Originally Posted by C2tuck View Post
Ok, so I've always wanted a wrangler and I finally got one. It's a 93 2.5 5spd. It's not perfect but I always like a project! I already plan on swapping a 4.0 in it and have already bought one. I'm sure ill be asking tons of questions when I get around to doing that

But my post for today is about it running bad. It runs fine until its warmed up and then it starts bogging down and backfiring bad! I'm talking downshifting to 2nd on the highway to get it to move. Never overheated or got close to being hot. I've already changed the plugs, wires, dist cap, rotor, oil and filter, and air filter. It was pretty nasty underwood so I cleaned her up a bit.

Any ideas?
Your emissions/fuel/timing etc. are controlled by the ECM. When the engine is cold are running in open loop mode and on the factory presets. Once the engine gets up to temp you go into closed loop mode and run on learned memory BUT you sensors are always checking those numbers. You have something that is out of the factory parameters.

idaholtby mentions checking for any stored codes. That is step #1. Does your Check Engine Light go on when you start your engine? If not someone pulled the bulb. You have to check for stored codes even though the CEL may not be lit up. If it does light up check your DTC's (trouble code by doing the following:

Post #3;
http://www.jeepforum.com/forum/f12/e...eading-311539/
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Unread 06-27-2013, 10:34 PM   #4
04WJny
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Does it backfire under load or at idle after its warm?
What size are your tires? stock? My engine is different than yours, but I find that when sometimes im on the highway and im trying to accelerate, sometimes i backfire because i put my jeep under too much load, especially with stock 3.07 gears lol.

Have you checked your vacuum lines? most importantly your vacuum advance on your distributer. You can use some carb cleaner and spray around the vacuum lines when your engine is running, if your RPM changes you have a vacuum leak.

Good luck with your new Jeep and welcome!
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Unread 06-28-2013, 08:33 AM   #5
mike_breaker_5
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plugged cat or muffler.
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Unread 06-28-2013, 10:28 AM   #6
Siva283
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Quote:
Originally Posted by mike_breaker_5 View Post
plugged cat or muffler.
^^^^This, Usually a bad 02 sensor running rich will cause the cat to melt. So if you do in fact discover its the cat change your 02 sensor.
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Unread 06-28-2013, 11:38 AM   #7
Kuntryboy816
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Congratulations on your first Wrangler!

What you are experiencing is called Testeronic Deflation. You aren't actually hearing a backfire but the sound of the afterburners failing to ignite which is pretty common with a 4-banger Wrangler. You have the downshifting part correct but I'd bet the PO didn't remember to tell you the last 2 crucial elements that will enable your Jeep to perform correctly... giving you that white-knuckled, nut-tingling euphoric rush of adrenaline that is called JEEP! First, when entering the highway, you MUST have Kenny Loggins' "Danger Zone" playing on the stereo as loudly as possible w/o distorting the sound. Secondly, when you downshift into 2nd gear you must quote (verbatum and in an excited manly voice), "It's time to kick the tires and light the fires!" The second you finish the quote, downshift into 1st, throttle to the floor and hang on!
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Unread 06-28-2013, 11:41 AM   #8
laybackman
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Quote:
Originally Posted by mike_breaker_5 View Post
plugged cat or muffler.
I agree that a plugged cat/muffler or crushed tailpipe could also be the OP's problem also but seeing if there are any stored codes or that his CEL even lights up will help us help him.
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Unread 06-28-2013, 02:42 PM   #9
ForestJeep89
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Quote:
Originally Posted by laybackman View Post
Your emissions/fuel/timing etc. are controlled by the ECM. When the engine is cold are running in open loop mode and on the factory presets. Once the engine gets up to temp you go into closed loop mode and run on learned memory BUT you sensors are always checking those numbers. You have something that is out of the factory parameters.

idaholtby mentions checking for any stored codes. That is step #1. Does your Check Engine Light go on when you start your engine? If not someone pulled the bulb. You have to check for stored codes even though the CEL may not be lit up. If it does light up check your DTC's (trouble code by doing the following:

Post #3;
http://www.jeepforum.com/forum/f12/e...eading-311539/
^^^^ this== remember always do the simplest things first cuz it usually saves a person a lot of grief...
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Unread 06-28-2013, 02:48 PM   #10
laybackman
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Quote:
Originally Posted by Kuntryboy816 View Post
Congratulations on your first Wrangler!

What you are experiencing is called Testeronic Deflation. You aren't actually hearing a backfire but the sound of the afterburners failing to ignite which is pretty common with a 4-banger Wrangler. You have the downshifting part correct but I'd bet the PO didn't remember to tell you the last 2 crucial elements that will enable your Jeep to perform correctly... giving you that white-knuckled, nut-tingling euphoric rush of adrenaline that is called JEEP! First, when entering the highway, you MUST have Kenny Loggins' "Danger Zone" playing on the stereo as loudly as possible w/o distorting the sound. Secondly, when you downshift into 2nd gear you must quote (verbatum and in an excited manly voice), "It's time to kick the tires and light the fires!" The second you finish the quote, downshift into 1st, throttle to the floor and hang on!
Naw, you only get that when you get married...or is that testeronic separation...I forget already.....
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Getting older, I have developed some special skills. I have the ability to cough, sneeze, fart and pee at the same time.

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Unread 06-29-2013, 09:26 AM   #11
C2tuck
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Thanks for all the reply's guys. I've been busy at work and haven't had a chance to reply.

1. The check engine light does NOT come on when I start it up...so I guess I'll have to check the bulb.
2. I'm about 30 miles from the closest auto parts store so I'm kinda hesitant to drive it that far to check the codes. Unless there is a trick that doesn't require a code reader.
3. The exhaust sounds like ****. It rattles and is pretty rusted. Can't see and obvious holes in it but I wouldn't be surprised if the car or muffler where clogged. If so would it not affect performance while engine is cold?

I don't really want to redo the exhaust now before I swap the motor in a few months...unless I can use the same exhaust with the I6.

Oh...and ain't no lightin' tires on this thing. It sees a hill and slows down!
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Unread 06-29-2013, 10:19 AM   #12
mike_breaker_5
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if the exhaust is rattling i say it's definitely a plugged cat. the ceramic cake comes loose and gets lodged in there sideways. i had exactly this happen to me on my way to work one day.
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Unread 06-29-2013, 12:27 PM   #13
laybackman
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Quote:
Originally Posted by C2tuck View Post
Thanks for all the reply's guys. I've been busy at work and haven't had a chance to reply.

1. The check engine light does NOT come on when I start it up...so I guess I'll have to check the bulb.
2. I'm about 30 miles from the closest auto parts store so I'm kinda hesitant to drive it that far to check the codes. Unless there is a trick that doesn't require a code reader.
3. The exhaust sounds like ****. It rattles and is pretty rusted. Can't see and obvious holes in it but I wouldn't be surprised if the car or muffler where clogged. If so would it not affect performance while engine is cold?

I don't really want to redo the exhaust now before I swap the motor in a few months...unless I can use the same exhaust with the I6.

Oh...and ain't no lightin' tires on this thing. It sees a hill and slows down!
If the CEL had a good bulb that did not light up when you hit the ignition your Jeep will not start UNLESS all the emission's equipment has been disabled.

Check the CEL bulb. I'll bet it is pulled. Steal another bulb out of the dash for the time being and stick it in the CEL bulb socket. It never blows since it is quite heavy duty. Once it is replaced go to this thread post #3 I think it explains how you can read the codes;

http://www.jeepforum.com/forum/f12/e...eading-311539/

Then for the codes go to this thread post #2

http://www.jeepforum.com/forum/f12/r...estion-723082/
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Chicks dig me.....Fish fear me

Getting older, I have developed some special skills. I have the ability to cough, sneeze, fart and pee at the same time.

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Unread 06-29-2013, 12:35 PM   #14
Masta-P
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My 93 4 banger had similar problems a few months ago. New cat straightened it out and if I remember correctly same part number for the 4 or 6.
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Unread 06-29-2013, 12:56 PM   #15
laybackman
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Quote:
Originally Posted by Masta-P View Post
My 93 4 banger had similar problems a few months ago. New cat straightened it out and if I remember correctly same part number for the 4 or 6.
The cat converter can often be the problem.

But the first issue is the OP's YJ starts but it show no CEL during startup.....I smell 'cover up' by the PO. You know the drill....no CEL..... nooooooooo proooooblems!!

And bet is there is a DTC that will show up when the OP gets the CEL bulb to light up. From there maybe we can figure out what is going on without throwing a bunch of parts at this YJ.
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Chicks dig me.....Fish fear me

Getting older, I have developed some special skills. I have the ability to cough, sneeze, fart and pee at the same time.

"If we cannot afford to take care of Veterans, then we should stop making them."
David C. Wilker Jr. USAF (RET)
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