Ok, so I finally decided to replace my exhaust manifold because there was a big crack in one of the welds and it was starting to sound pretty bad. I got the new manifold in and spent all day replacing it.
Just tried to start it up and the RPM shoot way up so fast that I just hurry up and shut it off. I know that If I did not get the Intake manifold on perfectly that the engine will not be able to draw a vacuum and that will cause the RPMs to go up, but I totally checked the placement (I thought) like multiple times to make sure it was attached properly.
I am very frustrated and before I totally dismantle this thing again to basically start over, I wanted to defer to the infinite wisdom of all the Jeepers on this forum..... :)
Does anyone know of anything else I may have screwed up or maybe need to do, before I totally redo this job......ugh.
Its a 4.0L engine, and I bought that new style manifold with the bellows for expansion that will supposedly work better.
05-17-2010 08:11 PM
Double check any vacuum lines you may have disconected.
05-17-2010 08:34 PM
You have to re-seat the manifold, somewhere it is not properly seated on a stud.
05-18-2010 07:16 AM
Thanks for the info guys. Was hoping I maybe did something stupid that I was too tired to realize at the time. Guess I will be starting over this morning... Hopefully I can figure out whats up with the manifold.
05-18-2010 10:25 AM
Ok, so I took it all apart again and reassembled it, and its still shooting up to like 5000 rpms. If it was just small leak in the intake manifold wouldn't it just be a little bit higher rpm idle? Am I correct in thinking this? 5000+ rpms seems really high, almost like there is a big gaping hole somewhere. The intake manifold looks like it is seated, I messed with it for a while before reassembling it this time, and I dont know how I would be able to get it any better. Is the gasket to thin maybe??
05-18-2010 08:30 PM
Look at the exhaust manifold from underneath the jeep. There are two pins that it has to seat onto otherwise there will be a pretty noticeable gap (like 1/8" to 1/4" inch) between the manifold and the block. You won't see it from up top. The pins can be tricky to seat sometimes.
05-19-2010 10:44 AM
Third time is the charm I guess. This time I loosened up the exhaust manifold while placing in the intake manifold and it popped right into place. I could tell as soon as it did that it was correct. Got the jeep back together and it runs fine now. Thanks guys.