[Boghog]

The idle air control (IAC) valve adjusts the amount of air allowed into the engine at idle condition and during rapid engine deceleration. This adjustment is done by means of an adjustable duty cycle output by the power-train control module (PCM). The PCM increases the duty cycle based on different inputs such as RPM, load and others.​

 

[theoldwizard1]

Vehicles with electronic throttle control do not have an IAC.

 

[easterwabbitonearth]

i never really thought about it but this part is probably what keeps the engine from quickly returning back to idle speed when you rev it up, etc.

as this part ages and gets carbon gummed up the idle quality can go bad and also can be too low etc,

i like to remove and clean mine at least once a year, and also the hole in the TB unit it threads into,

clean out all the carbon with carb cleaner and compressed air

and do the same with the valve

clean out the IAC plunger spring and shaft real good, of all the carbon and gum

if its having bad idle or low idle speed then try this.

its a pretty common issue

ford dodge and gm all use these.,