The clicking and clacking you describe may be your injectors firing. They can be audible. IAC (idle air control) is normally inaudible unless doing a key on, engine off test with scan tool. The IAC controls idle air flow. For the most part it is static but if ac compressor kicks on or you shift from park/neutral to R or D then IAC is going to compensate and adjust idle for the load on engine but only at idle. When throttle plate is closed there is no clearance around the plate to throttle body so no airflow around throttle plate. The IAC is a path around throttle plate. The pintle is part of IAC, basically a valve that is stepped in or out by IAC. In essence, it's an electronically controlled valve. Simply, the IAC is an electric motor controlling a valve referred to as a pintle valve or just as pintle. It adjusts airflow around throttle plate and compensates for engine load at idle.
Did I say the same thing like four times? Seems like it to me. Just trying to say it different ways and make it not confusing.
