If you have quite a lot of gas coming out there then it is probably flooding. Smaller amounts are caused by a worn shaft hole. The worn hole will make the shaft loose and give a rough idle from time to time. There are shops that can install bushings in it to fix the problem.
Would the rough idle be accompanied by a audible vacuum leak? The shaft hole didn't seem bad, but yesterday I was driving the truck up and down the driveway and after a while the idle went rough, and I could hear a sucking noise. I didn't get a chance to look into it, but it would make sense that was the problem.
