as the 2001 outback warms up it get worse rpmsjump up and down quite abit on 2001 Subaru Outback

rpms drop to 500 maybe lower at stop eng. stumbles when trying to leave a stop then jump up hard and fast in cruise control can will startto slow then rpmswill jump up 1500 or more for car to speed up to set speed

2 answers
could be coked throttle body or poss idle air control valve

Idle Air Control valve is most likely the culprit