The IAC is a linear soleniod plunger type located on the intake manifold, the purpose is to control the amount of intake air flowing from the IAC passage. The IAC valve is driven by the duty cycle signal from the ECM.
You might want to check the electrical ceonnections, if found OK, you will need to verify that air passages are not plugged or that the soleniod valve is OK.
There is also a procedure for adjusting the air flow bypass that control tidle speed.
Good lock in finding your problem.