and no you can't adjust the iac. what an iac is is a valve that is actuated by a motor that opens allowing air to bypass the throttle plate at idle to keep the car running with no throttle. what happens is the motor gets weak over time, or the valve gets clogged with carbon and sticks, causing an erratic idle concern. one easy way to tell is when your idle shoots up tap the motor with a screwdriver or something and see if the idle returns to normal (doesn't work ALL the time, but it is a sure way to tell that's what the problem is if it does work). the only way to permanently correct this is to replace the iac.