is it the trany or speed control senor the cars rpms go up to 4000 and races on 1997 Ford Expedition

when driving but comes back down when you hit the peddle

by in Staten Island, NY on December 10, 2012
2 answers
ANSWER by , December 10, 2012
sounds like idle air control or poss vaccum leak. do you have a ck eng light on?
ANSWER by , December 10, 2012
possible IAC issue