1993 Buick Skylark Idleing

My car is having an irregular idleing when it is in park or neutral. I also notice a (for lack of a better discription) a natual gas or propaneish odor). I believe it could be associated with an air control valve. If it is, how do I access it on the engine and is there an easy first thing to try before I take it to a repair shop?

Thank you.

Kevin Cummings