Accel function often delays before works. Have to hold it on X time to accel. If you "bump" it when on but inactive, Resume set speed after using brakes.
get owners book at http://www.fieronews.net
While book say Tap-up/down when on and active = add/minus 1mph often doesn't work for many. Not sure why but doesn't. Might be iffy switch, user timing to use this or both or other reason(s).
If still won't work and everything thing else works then
See my Cave, Cruise Control
and check "pins" A - C turns on and A - B stays on when system is on as you push accel.
Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should.
The Ogre's Fiero Cave