I was wondering where the IAC is located on my 1999 GMC 5.3. I was also wondering if a problem with it would cause my trucks idle to drop to below 500 rpms when i put it into gear then before dying shoot back up to the normal 500 rpms. If its any help the truck idles fine if not a little high when you first start it up in the morning then after idling for a while it levels out. I was also wondering if I would need a new IAC if thats the problem or what to do to fix the problem. I have already cleaned the throttle body with cleaner.