Changed exhaust manifold. Now hesitates and surges. - Jeep Wrangler Forum
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Old 05-26-2011, 09:44 PM   #1
Join Date: May 2011
Location: Indy
Posts: 3
Changed exhaust manifold. Now hesitates and surges.

I replaced a cracked exhaust manifold on my 99 TJ 4.0 6cyl. The entire exhaust system is new. This problem did not exist before the repair. It ran pefectly for 15 minutes and then began hesitating and surging forward. I have driven it three times since then. It starts out with the same problems but much less severe and seems to heal itself for 15 minutes but then comes back for a few minuets. No check engine light comes on. I did all this work myself and I am not a mechanic. When I reassembled the fuel rail I did not do anything to bleed air out of it, and it was bone dry when it went back in, is that what's wrong?

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Old 05-26-2011, 11:29 PM   #2
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Join Date: Nov 2010
Location: South East PA
Posts: 379
Could be that your 02 sensor isnt working right after being moved around or bumped and causing the engine to not get the proper Fuel to air ratio.

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Old 05-27-2011, 12:04 AM   #3
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Join Date: Dec 2006
Location: For-8-Oh!
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Replacing the exhaust, when done right, doesn't require the fuel rail to be removed from the intake. I doubt there is air in the rail as it would easily be forced out after running. Are you sure the exhaust manifold was seated properly on the head? There are 2 cast points that protrude out that help align the manifold.

Also check to see if there are any broken vacuum lines or if any happen to get disconnected. Another item to look at is the MAP sensor. This sensor can cause problems like you are talking about, and had that issue before on my XJ.
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Old 05-27-2011, 05:22 PM   #4
Join Date: May 2011
Location: Indy
Posts: 3
Thanks for the advice. I drove it to Indy today and it cleared up for the entire drive home. I think I am ok now. I'll have the hood back up after the weekend and I'll check those things out. AzTJ to not disturb the fuel rail could I have lifted the intake up rather than pull it out the the doghouse completely? I was following my Haynes book to the letter but was not looking ahead to make sure each step was really needed.
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Old 08-30-2012, 05:52 PM   #5
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Join Date: May 2012
Posts: 151
I know it been over a year but i just changed a manifold, now i cant start either. I know im not getting fuel to the rail. i was thinking it was a bleeding issue too? any help?
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