well about 2 months ago my idle started rising up and down from 500 to 1000 when i stoped. It progresivly got worse until it got to the pont where id let of the gas and it would keep going like it was on cruise. so i figured it was the idle air control valve. i replaced that about a month ago and all was well for a couple weeks now its starting to do it again. someone suggested seafoam so i tried that and that worked for about 5 days. what should i do?