Its located usually on the inlet manifold. Its basically a servo for control idle and is normally black and round bodied. Heres an ebay link to the one i think is fitted to your car
http://cgi.ebay.co.uk/NEW-Idle-air-c...item3c9f4c0c7a
Just strip it off and blast with carb cleaner (bearing blaster or nitro cleaner) If that doesn't do it, then check for air leaks around the brake servo, inlet manifold and vacumn hoses.