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Unread 07-09-2010, 05:59 PM   #1
jwhite1071
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slight idle issue after exhaust manifold replacement

Hey everyone, my first post and I'm asking questions already.......sorry, I apologize in advance!

I changed out the exhaust manifold yesterday because it was cracked and was driving me nuts. Now its idling around 850-900 when in park.....now this is driving me nuts. I know its real easy to get sloppy or careless on this job which can and will lead to a leak however so slight and cause an idle issue but I'm pretty sure I was extremely careful and paid attention to detail when doing the job because of this.

I bought one of the $99 ebay manifolds, used a mopar gasket, cleaned the block and intake to perfection, sprayed the gasket with copper, made sure the maifold was seated on the dowls, torqued the bolts in proper sequence to approx. 23-24 ft. lbs, re-connected everything as it was, cleaned the TB and replaced 4 of the six injector o-rings. Vacum lines look good, I've sprayed the intake with cleaner while its running to check for a leak.......got nothing noticable. The only thing I can think of was I reused the TB gasket because it was fairly new and looked great ???..........any thoughts or ideas guys are greatly appreciated.


Last edited by jwhite1071; 07-09-2010 at 07:31 PM..
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Unread 07-09-2010, 06:18 PM   #2
Unlimitedlou
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Sounds like you have covered everything. I would drive it a little bit and see if it changes. The computer may have to relearn your new manifold. You also could flash your computer. There is a couple of threads on it. I can't remember exactly how. I have tried it a couple of times after performance upgrades and can't really say if it works or not. Good luck.
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Unread 07-09-2010, 06:48 PM   #3
jwhite1071
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Thanks Lou, I'll give that a shot
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Unread 07-09-2010, 07:03 PM   #4
Unlimitedlou
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Good luck!
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Unread 07-14-2010, 02:02 PM   #5
jwhite1071
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Just a quick follow up incase anyone has a similar problem..........

I put about 200 or so miles on the Jeep and the idle actually got a bit worse to about 1000 - 1100, so I decided to check over everything again, found 1 injector o-ring missing??? (no clue where it went) and two others sliced, I replaced them and she runs perfect now. I guess a bit more finess could be used when re-installing them.......oh well lesson learned.
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Unread 07-14-2010, 02:45 PM   #6
DevilDogDoc
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And tha was why the last one that I did over the weekend I left the fuel rail attached to the intake and just flipped it over upside down...
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Unread 07-25-2013, 03:20 PM   #7
sreilly1
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I have similar issue

I just replaced my exhaust manifold as well. My idle now wants to redline as soon as i start it. What did i do wrong? Help!
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Unread 07-25-2013, 03:54 PM   #8
Jerry Bransford
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Quote:
Originally Posted by sreilly1 View Post
I just replaced my exhaust manifold as well. My idle now wants to redline as soon as i start it. What did i do wrong? Help!
That's an easy/common problem, you didn't get the intake manifold properly reseated so it is now the source of a huge vacuum leak. Unbolt the intake manifold & with known good gasket, take a little more time this time to insure it is properly seated over the positioning studs on the head.

Assuming you have the vacuum line from the intake manifold to the master brake cylinder reconnected which would cause the same redline RPMs.
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Unread 07-27-2013, 11:41 AM   #9
sreilly1
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Thanks and u were absolutely right. Got a mirror and checked the pins. They were a little off. That's what happens when a non mechanic does the job. Pretty east though to loosen the bolts, realign the pins and re-torque. Running perfect now. Sounds great too with the new (used) exhaust manifold. Thanks again. I couldn't have done this without YouTube and you guys!
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exhaust header , exhaust manifold , fuel injector , header , high idle , idle , injector , manifold , o-ring
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