Engine REVs high at start after manifold replacement :confused: - JeepForum.com
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Unread 01-09-2011, 10:06 PM   #1
GDM97TJ
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1997 TJ Wrangler 
 
Join Date: Feb 2006
Location: Southern Pines, NC
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Engine REVs high at start after manifold replacement :confused:

I just replaced the exhaust manifold on my 97 TJ 4.0. Whenever i start it now the engine just REVs like someone is stomping on the Gas. i'm not sure what would cause this but i ran into a couple other problems as i was putting everything back together that might be helpful in helping me figure this out.

When i put the power steering pump back on the bolts didn't line up through the bracket and into the intake manifold, so i had to unbolt the bracket from the block in order to get the power steering pump screwed into the intake manifold. then the serpentine belt would not fit around the power steering pump pulley, even when the idler pull/tensioner pulley was fully extended; i ended up having to use a pry bar to get the belt around the pulley and even then its still not completely on.

I'm assuming that when i put on the intake manifold i must've not seated it fully or correctly and that is somehow contributing to the immediate high acceleration when i start the engine. i've checked the accelerator cable and it's not stuck open at all, so i don't think that is the problem.

i'm hoping someone might know what i did wrong before i have to strip the whole thing down again. so any advice or ideas anyone could lend would be greatly appreciated.

oh, and using a torque wrench on those manifold bolts is practically impossible, i don't see how you're supposed to get a torque wrench in some of those tight fit spots.

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Unread 01-09-2011, 10:38 PM   #2
NakedJeeper
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1998 TJ Wrangler 
 
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Vacuum leak is the most likely source. Since you had bolt alignment issues, maybe the manifold isn't seated well.
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Unread 01-09-2011, 10:39 PM   #3
CJ7-Tim
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That's the most common symptom of a massive air leak at the intake manifold. Re-check your work, either the intake manifold is not fully flush to the head or you forgot to reattach one of the vacuum hoses.
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Unread 01-10-2011, 07:18 AM   #4
iceman6533
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i had this happen the first time i replaced my exhaust manifold, and wound up cracking the intake. make sure the intake is lined up on the 2 dowel pins on block at each end of the intake. once you have the intake back on try to hold it flush up against the block and try to slide it STRAIGHT up, you should have about 1/8" of play up and down, if it comes up off the engine it wasnt on the dowel pins.
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Unread 01-10-2011, 07:25 AM   #5
iceman6533
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also i have found that using a u-joint in between the socket and extension (6 inch on the bolts closer to the ends and a 9 inch on the inside bolts) works best. reach under the intake with the socket/u-joint/extension (off the wrench) and put it on the bolt head and hold it there, then install the wrench on the extension and torque to spec. if you have someone helping you, have them get under the jeep with a flashlight to help you get the socket on the bolt head (also can have them stick their pinkey finger in the dowel pin hole to see if it is lined up properly)
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Unread 09-30-2014, 11:58 PM   #6
greekroman
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I'm having the identical problem. I have already re-installed the manifolds for the second time and i still have the high revving at start up. My vacuum lines seem to be ok so i have to assume I'm not lining up the intake manifold properly. I looked at where the intake manifold seats on block and it is touching on the top edge but slightly off as you go down . I think the problem is that I didn't hold the manifold tight and square onto the block as I tightened the bolts . I assumed the manifold would seat square as I tightened it but its not happening . I'm going to try again and focus on keeping the manifold square onto the block as I tighten and also on those alignment pins . Regarding torquing the bolts i just torqued them by feel because like you said there's no way to get a torque wrench in that clutter. A friend of mine said that they should be torqued to about the same force you use when installing a spark plug . Something I did to help line up the lower bolts is I marked their location vertically on the valve cover so i had a target when trying to get them onto the wrench socket. I will let you know how I make out tomorrow.
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