When my car is warming up, and even a little while after the coolant is warmed up, the idle does this wierd up and down thing. It'll go between 1,000 and 1,500 rpm's, it'll kind of rev up then just drop back to 1,000, then rev up and drop, over and over and over. It didn't do this when I first got the car a month and a half ago, just started about 2 weeks ago. Did something come unplugged or something? Seems like everything is plugged in, nothing looks out of place. Anyone had this problem before? It goes away after driving it for a while, and pretty much only does it after it's been sitting for 8+ hours, basically when it's cold(even though it's definetly not cold here).

Any idea's?