A good working IAC will hold idle after raising it up past its normal idle point upon starting the engine.

Excess air from any place behind the AMM screws all of the up!

Check the accordion tube behind the AMM for any crack or small hole in it first.

Look for bad vacuum hoses or loosely connected ones.

Clean the throttle body and check the throttle switch adjustment. Making sure the throttle plate is closed completely at the same time the switch is clicking into closed idle position!

I would leave the AMM alone unless you can tell it has been doused in engine oil from the large hose or something crazy like that. There is a very fine wire inside the middle cone that you do not want to harm at all!
A good air filter should be all that's needed to keep it in good working order.
It's something that a direct blast from a compressed air hose or even a plastic spray can tube blaster can have it toasted in a flash!

If there is still a heater door& thermostat in the air box, get rid of it. The excess exhaust header heat destroys an AMM!

It all snaps out on most cars. It can be made to block the stove pipe tube if you want to leave that on there for those very "passive" and "glazed over eyeballs" kind of state inspections.
I use a 5/8" square block of anything solid to hold it over the hole.

Phil