wierd idle

[cb96]

hi, i have a 96 jimmy and every so often it idles wierd. i'll go out to start it and it will start idling at 1200rpms. it then slowly increases until it reaches up over 2500rpms at idle. it will keep increasing until the vehicle is turned off. then on the next start up, it will idle fine. what could this be?

 

[10r]

Ok so I'm not good with the exact terms but.......I would look at the AIS motor or idle air control. It will be on the throttle body usually held on by 2 screws. it control air flow to your engine at idle. Take this off and clean it with throttle body or carb cleaner. They get gummed up.
let us know how it goes.