Missing, backfires on acel, rough idle...help?! - JeepForum.com
 
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post #1 of 6 Old 01-21-2016, 10:34 AM Thread Starter
Notverycreative
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1997 TJ Wrangler 
 
Join Date: Dec 2014
Location: Daytona Beach
Posts: 29
Missing, backfires on acel, rough idle...help?!

Yess, i've searched a lot and tps (replaced) was closest to alll my symptoms

Ok, so here's the deal...

I have a 97' TJ 4.0L 5sp trans. Re manufactured engine (473 miles on it) Initially had a re manufactured head on it that was defective causing similar issues along with overheating (typical blown head/gasket symptoms) Replaced that, no more over heating but it still idles rough (at 1300rpm, with slight missing sound, slow to drop rpm after rev, and more annoyingly backfires/sputters on acceleration, this primarily occurs at 2k rpm as if there were a "flat spot" and always backfires at that rpm. 2nd and third gear being the worst. once i give it more throttle is clears up (which is why i thought it may be fuel related)

I've reset pcm, unplugged 02 (no change) Installed new TPS, everything to do with ignition is new, no dash light codes other than 12. there is good fuel pressure/pump kicks on.

My headers are cracked (who's arent?) new one just came in today, but may not get on with this weather..& assuming that wouldn't cause ALL of this though, at least without emissions code? IAC and MAP are my other thoughts, however IAC would only cause a rough idle, right? Anyone ever experience these symptoms for the MAP?

Also, most likely not connected, once the heep warms up, gears ger sticky..cant get it into 1st and second is hard from stop.. installed new clutch with motor, but didn't bleed other than pumping the &%^# out of the clutch lol.

If ive missed any info call me out for it! & Thanks in advance for any help!

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post #2 of 6 Old 01-21-2016, 11:32 AM
Jeepsr4me
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When you replace the header you may find a the vacuum leak.. cause that is what it sounds like to me.

Be mindful of all the hoses and inspect them when you pull the intake off. Replace any that are hard AND if they show any signs of cracks ... Even the grommet in the valve cover,,,, Getting that elbow out is very hard to do if that grommet is hardened.
I take a heat gun to it and then the elbow pops right out.
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post #3 of 6 Old 01-21-2016, 12:53 PM Thread Starter
Notverycreative
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1997 TJ Wrangler 
 
Join Date: Dec 2014
Location: Daytona Beach
Posts: 29
I started to lean into that, the front grommet is missing (have a little air filter lookin thing there) and the rear one has a straight piece of tubing ran to it due to breaking the previous one. i'll go through em today, thanks!
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post #4 of 6 Old 01-21-2016, 01:28 PM
Jeepsr4me
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Thats your problem... You need vacuum on both././.
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post #5 of 6 Old 01-21-2016, 08:22 PM Thread Starter
Notverycreative
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1997 TJ Wrangler 
 
Join Date: Dec 2014
Location: Daytona Beach
Posts: 29
Okay, so Autozone actually carried the Elbows here! which is awesome, because ive never been able to find them anywhere but online for my tj or yj!

Now, the idle is MUCH better, it sounds healthy! I can't believe i was told i could just put an air filter on there and it would be good.. Well, i can't believe i didn't know better haha. Thanks!

The jeep is still missing/popping on accel though.. I got two codes after fixing vacuum, idk if it was hiding them or what..but it's 21 & 31, 31 is A/C clutch relay blah blah, don;t think it really matters? I have no A/C unit lol. Then 21 is O2, i unplugged both O2's and ran it a bit. it may be in my head, but seemed to run better? However was still missing on acceleration. Ideas?

Probably a stupid question, but i'm only an A & B mechanic.. my belt squeels and is kind of loose..That couldn't cause backfire like that though right? Just engine cut outs at most?
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post #6 of 6 Old 04-03-2016, 04:33 AM Thread Starter
Notverycreative
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1997 TJ Wrangler 
 
Join Date: Dec 2014
Location: Daytona Beach
Posts: 29
Late on the repost, I've been busy..but to help anybody with this problem in the future, I have changed the tps, IAC, with no luck..so I went ahead and put on a new exhaust/headers. Turns out the cat/muffler was clogged. As far as that particular issue, it is resolved.
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acceleration , backfires , misfires , rough idle , sputtering

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