rough idle

I have a 01 Sunfire 2.2L. It has a really rough idle when the the car is stop. (Kind of like a misfire but not quiet as bad.) Once I take off it's like there is no problem until I stop again. I went to my trusted mechanic and he couldn't find a problem with it. He told me it could be the IAC valve or the spark plug wires. The wires are only a couple of months olds but i went a head and replaced them and the IAC valve. Still the problem consists. Also there are no engine codes. The wear on the spark plugs are all the same and they're less than a year old. Next I'm going to change the fuel and see if that helps. Has anyone had problem like this and fixed. If so any info will. Thanks for your time.