I recently finished the motor swap on my XJ. I got a used 98 wrangler 4.0 with 127,000 or so claimed miles on it. I tore it down to long block and replaced all the seals. From the rear main up. I got it back in my XJ got the distributor set and it runs like a top. Other than my dad didn't put the four bottom intake/exhaust Combo bolts in and I drive it for a day with our them. He asked to help so I figured you can't **** that up... Lol I was wrong. Anyways now when I put it park my resting idle goes to 1200 rpms and on start up it climbs to 3500 for a second and the recesses. Any ideas why this might be?

 

I meant short block. Head gasket and everything. Geeze it's early

 

It must be early because you didn't include the year of your XJ in the post or fill out your profile.

 

Put all the bolts in and see if it fixes it?

It also sounds like it could be a dirty IAC valve?

 

Possible that the intake/exhaust manifold gasket is warped or not sealing properly from running around like that. When you replace that normally it's pretty important to torque the bolts evenly and then re-check every few days.

 

u need those bottom bolts

 

I have since put the bolts in after I found out they were out and I thought maybe it could have been the IAC but I was checking in here to see if that was a common mishap. Sorry for the lack of info on my part I am new at the forum thing now that I finally have a vehicle worth joining a forum for.

 

I also must say that my jeep is also a 98 and I cleaned the throttle body vividly before returning it to the manifold.

 

You need to torque them in a certain pattern. By doing the top then bottom, you created unevenness.

You might be able to get away with just loosening them and torquing in the proper pattern, but the gasket could also have formed to what you have now.
Check the less time consuming things now, IAC, TB. And in 500 miles regardless retorque the bolts for the manifolds.

 

Roger that. Thank you everyone for your responses and help. On another not I will update my profile and get some pictures up for you guys.

 

Pictures are always good!

 

Well gentlemen today I took the intake/exhaust manifolds off to look at gasket and see if I could reuse with proper torque pattern. As I was inspecting the gasket I could see that the outline from the intake manifold and it was larger than the ports available from my manifold. I bought the gasket kit from mopar. Terrible idea. I imagine that the kit I got was for a 00/01 but I don't know. But that was what was wrong the gasket port was large enough to leave a gap between the intake manifold and the head. Mind Blown!!! But that is what I get for not inspecting things more carefully

 

Hmm that rings a bell now... one of the heads the XJ was rolled with has a combined port for certain cylinders, doesn't it?

 

So here's the bottom line: you used your old head from XJ, right? so that's all it matters.
Sounds like you got the wrong size gasket.