extremely high idle after header install!

[BIGSLVRXJ]

Yes - I did see that clearance issue regarding the #6 intake and exhaust header. I couple of guys said they had no issues, so I thought I was lucky - guess not.

When I mounted the intake it seemed to slide right into place -felt nothing hitting.

What I need is a 3 day weekend so I can take it apart and check everything again - gets dark too early!

I know when I first tried it, the intake wouldn't even bolt on it sat at such a crooked angle. It's possible you got lucky and that's not the issue. If that's not the issue though, that would mean you have a pre 99 intake on your 99 because the 98- style fits fine but any of the rounder 99+ intakes will not fit without some material removing.

 

[Harlee&Tahoe]

I have a '99 and I just finished installing an APN header and Dynomax cat back (and Brown Dog motor mounts) this weekend. I've just started the XJ for testing and have an extremely high idle - 5,000 - 6,000 RPM, like I was flooring the gas except my foot is off the pedal. It'll run at 5K, but I get worried and shut it down after 20 seconds or so.

I've checked the throttle lines and return spring and everything apprears correct. The butterfly in the throttle body remains closed. All my sensor connections and vaccuum lines have been reconnected and are snug.

I followed Go-Jeep's instructions and the FSM - the install went without a hitch (did not need to clearance #6 intake as others had to). Only modification was to use a FelPro gasket instead of the APN one.

Everything ran normally before the install - just had to fix exhaust manifold crack and figured to replace the exhaust and motor mounts while I was in there.

Any suggestions are appreciated.

I can't believe no one has pointed this out yet. You cannot use an APN header in conjunction with the 99+ intake without clearancing the #6 cylinder tubes. What you have is a major, major vacuum leak because the intake isn't seated against the head. You have to take the intake back off and grind a bit of material off of each the intake and exhaust on the #6 runner. Search on :: here...you will find a thread that talks about the interference and tells exactly where to grind. Good luck!

Sounded like he's aware of this issue and wasn't a problem.
I however agree that is likely the problem.
However, I'm still NEWB and always will be and will never claim to be anything more.:kissyou:

 

[BIGSLVRXJ]

Sounded like he's aware of this issue and wasn't a problem.
I however agree that is likely the problem.
However, I'm still NEWB and always will be and will never claim to be anything more.:kissyou:

I understand that, but I can almost guarantee even though that didn't feel like the problem it is. It's a very tight area down in there and quite hard to see, but if there is even 1/32" of a gap there, you're going to have a major vacuum leak. And by the way I've never said newbs don't know anything so don't think that what a few people say is the consensus here okay?