I have '03 Express 3500 with a peculiar throttle body (TB).

The common TB has a 100mm air inlet and an integrated vacuum line connection at the top left behind the plate.
My TB has a 94mm air let and the vacuum line is mounted just behind the TB to the front of the intake manifold.




Would the location of the vacuum line connection be the difference in air inlet size?
Would it impact the IAC function? Or "if the IAC fits wear it?"

This is revolving around an idle issue and the IAC,
I have been trying to locate an IAC for my TB but what they are, is in a black hole.
There are plenty of IACs for the 100mm TB and couple odd named aftermarket parts for the 94mm.

Searching for the P# 20663 J1702L of the original IAC, a #17113598 comes up.
But all other reference to the #17113598 go back to the 100mm TB.

 

I don't know the answer to the question on the part numbers and the IAC valve.

It might be easier to just swap in the common 100mm throttle body with the IAC and be done with it.

 

Amen.
Wouldn't the 100mm throttle body have a different mounting pattern?
The people that make these things aren't big on providing dimensions.

 

I can't say for sure on this van but I would lean towards it having the same bolt pattern and harness plugs as long as it's from the same generation. My guess is that all or most of the truck engines in a generation share the same bolt pattern and plugs. This way they can use the same parts for as many applications as possible. I've swapped different size TBs on other vehicles with no problems. Even from different sized engines. This one is cable actuated which is good. Swapping drive by wire TBs is a little trickier since they might have to be programmed.

This would probably be a basic question in an LS forum.

 

Also, if you can look up the gaskets for the TBs they might be listed with a diagram measuring the distance between the bolt holes. Or you might find the gaskets are the same part #.
I bet the answer is out there in Google if you switch up your searches.