Jumping Idle on 91 P/A

i have just recently bought a 1991 Park Avenue. It has about 130000 miles on it. it runs great, but whenever i start it after driving it for a little bit, the idle will jump quickly up and down from about 800rpms to 1100rpms. What could be causing this, and what can i do to fix it?? Any help is greatly appreciated! thanks

Usual suspects:

Plugs and wires
Fuel filter

Less likely:
Coil pack
Injectors
Fuel pump/sending unit

How about carbon in the throttle body or Idle Air Control Valve?

How about carbon in the throttle body or Idle Air Control Valve?
i'll try all those suggestions, thanks!