Up under your throttle body is a little gold plate with 2 screws...take the plate off and there will be a little hub with 2 slots on each side. take a small screwdriver and spin the hub until it touches base with the spring. this should fix your problem!

If not, then it could be vacuum related so check all your vacuum lines and listen really close around your intake manifold, and throttle body. If either one of those gaskets are bad then that would also cause it.