It's supposed to move electrically, I believe it "twists" in and out. Take the IAC out of its housing, then have a buddy "key-on" the ignition, not start but key on. The plunger should retract, this would allow bypass air around the butterfly valve in the TB to maintain the engines idle. It will extend when you key off too, this happens also when you accelerate the IAC will begin to close and the air flows through the TB butterfly valve in place. Make sure it's not slow to retract/extend.