What year is your car?? When was the last time you tuned it up? Changed the air filter, distributor cap & rotor, spark plugs & fuel filter?? Ever SEAFOAM your intake??
http://www.youtube.com/watch?v=Ef3HNvxblxQ
Chances are you throttle body & IAV valve are dirty & just need a good cleaning. If you change out your air filter, distributor cap & rotor, spark plugs & fuel filter, tune up your car & Seafoam your intake, you'll notice a drastic improvement in how your car idles & runs.
Hope this helps....
ID