Topic: 4.0 throttle body question

[Lah2420]

I'm getting in the mood to play some more with my toy. I bought a 4.0 throttle body on line last week and started to clean it up and get ready to swap it when the heat goes away. Looking at it, the PO has JB welded something to the head of the screw under the throttle arm. It holds the butterfly open slightly. I thought the butterfly was supposed to be closed all the way at idle on these and the idle controlled by the AIS. I looked at the one on my 2.5l and it is just the threaded end under the throttle arm. No kind of head on it. Is the butterfly supposed to be open some? Or could the PO have had idle problems and did this instead of cleaning the gunk out of the AIS module? It was nasty.
I am going to swap the AIS housing and TPS from my 2.5 anyway.

[sharpxmen]

would be open 1/2 to 3/4 turn from the fully closed position on the adjusting bolt - you're right, should be open just enough so the butterfly to not catch/get stuck in the bore, everyting else is controlled by the IAC (Idle Air Control) Valve. Use the valve from your 2.5 liter including the housing, don't use the one that came with the 4.0.

[dwtaylorpdx]

+1 the 2.5 Air control valve is not optional,, the 4.0 will make you idle at about 2000 rpm(ish)

Dave

[Lah2420]

It would help if I got my alphabet in order wouldn't it? IAC---AIS---I think I'm developing Half-timers in my brain. Thanks. I'll put it on as is and see what's going on before I adjust anything-after I make sure he didn't jb weld the screw in.

[grumpygy]

Need to read this 1st.

http://4bangerjp.com/forums/index.php/topic,8.0.html

[SamsonJR]

 when swapping the IAC housing, Be careful not to destroy the gasket between the TB and housing, and clean it out really good. there's also a O ring on the IAC, make sure you don't lose it :)

[Lah2420]

Need to read this 1st.

http://4bangerjp.com/forums/index.php/topic,8.0.html

Thanks Grumpygy. I had read that and that's where I got the AIS acronym from. I do appreciate you taking enough interest to point that direction though. Better too much information than not enough.

[sharpxmen]

i've seen it used both ways (IAC or AIS), doesn't matter since we all know what it means, i think the more popular is AIS whereas IAC is the terminology used in the FSM.

[Jeffy]

I just use 'IAC' because it's what's used in by Jeep, so it's understood here.

[az_zoner]

I did the same mod and I bored the intake manifold to match the size of the throttle bore. Some people just use a dremel but I put it on a mill. If you have a steady hand you can probably achieve the same results.

cb

[Jeffy]

I did the same mod and I bored the intake manifold to match the size of the throttle bore. Some people just use a dremel but I put it on a mill. If you have a steady hand you can probably achieve the same results.

cb

The article first appeared in 2001.  There have been several people here who have port matched the intake.