2000 Ford Crown Victoria Very Odd & Random Problem

Hello, my 2000 crown victoria has given me very few problems, with the exception of this: Randomly while driving, the car will idle super high( almost as if im giving it gas, and even while im at a light at a stand still)for a matter of seconds, then it will bog back down super low for exactly one second(almost as if it is going to cut off), then it will return to normal? It will only do this once every time I am driving, usually within the first 10 minutes or so. It does NOT do this every time im driving. Well im scratching my head on this one, so hopefully you guys can help me out, oh yeah I tried giving it a tune up, i.E. New spark plugs and coil packs. Car runs a little smoother now, but the problem is still there lol )Thanks Guys!