just wondering what it is... i thought it was the idle speed adjuster... but i figured that out....

 

huh, looks like a blurry pic to me...

 

That large black screw controls the idle-up for the power steering pump and the A/C compressor on some models. The purpose is to allow for a bump in the idle speed while the power accessories are running and placing a load on the engine at idle.

 

Technically, it's called the "Idle-Up Valve", but for lame-man's terms, you can use carguygt500's definition


It works in conjunction with a vacuum valve on the power steering pump, as well as a VCV on top of the valve cover that triggers with the AC compressor clutch (if equipped with AC)


You will not find one on a truck with no power steering and no AC, as there's no need for the valve then, and there's just a plug there

 

where can I find one to replace mine