Question...driving truck normally, idles fine. Truck is at normal operating temp. Then the idle jumps up about 100 RPM. Its easily recognizable by ear. I hear it, then look down at tach, its at about 900 RPM. I shut it down, wait 20 seconds, then start it up again. Now its back to normal. This seems to happen more in winter months(not totally sure). Truck runs fine, otherwise. Is the truck running too cool therefore the motor automatically jumps up the RPM to get warmer? Any clues?

Thanks

 

If it is like mine, and many others. Whenever I come to a stop the truck drops about 100rpm every time. From what I've heard it's computer controlled.