Idle problem after replacing the timing belt

I just changed the timing belt to my car. I rotated the belt like I was supposed to. It started up fine on the first try. The next day it started and then ran for a few minutes and then it started to run rough I hit the throttle and it would almost stall then it would pick back up and run normal again. If I let it go it will start to idle down and then idle back up again runs for a minute then drops down again and picks back up again. It started to do that last year but would only do it on the first start or if it was cold out. Could it be my idle control or did I mess something up?