Ok, for the mechanics here. I just changed my header in my XJ. Put everything back the way I pulled it out. Now when I start it it goes straight to 4k rpms. To do the header I had to dismantle my whole intake. Any thoughts on why its doing that? I found out that I did have the break boost vac and the ccv vac mixed up. I put them in the correct places, but it's still running at just over 3k. The only other thing that I can think of is that after I cleaned the manifold it fell over onto the throttle body. It was only up on it's edge, but I don't know how sensitive those computers are to impact or whether I might have knocked a spring lose or something. Please help me out, this is my daily driver.

 

Manifold not seated on head very common it not down all the way onto head wedge/stuck on dowel.

 

Agree with freegdr; this is a very common problem. Causes a huge vacuum leak.

 

Make sure both manifolds are flush and the bolts are tight. The gasket will "settle" a bit and cause the bolts to not be tight anymore.

 

Sounds like the rear manifold breather line from the valve cover to the intake manifold is not connected.

 

This^^. VERY common.

 

Also make sure the exhaust flang is sealed good. I just went through this exact thing last week and found both to be not sealed very tight.

 

Thanks for your help. It looks like my manifold is sitting a little higher, on the bottom in the back, than my header. It will take me a couple of days before I can see if it fixes the problem. Lucky for my wife and I, we have two vehicles and work different ****.

 

You could also check the idle air control valve, it is somewhat spring loaded and if damage, could be causing your high idle. It is the circular attachment on the throttle body held on by 2 torx screws.

 

Not the issue here. A bad IAC will never allow the engine to rev to 4000 RPM.

 

Well the good news is that the only real issue was that I didn't have the bolts torqued as good as I thought they were. Thanks for all of the help.

 

Easy fixs are the best..

 

Yes they are.

 

TPS bolts?

 

Whatever the stock bolts are.