Terex 42

I've got a 2001 Terex 42 boom lift with Ford Gas Motor: Everything works great but when I extend or retract the basket it stalls often. A few times when I push the foot button it revved the motor to a higher RPM which it should do so the added action of extending or retracting doesn't stall out. Is that a loose wire or adjustment that won't let it rev when needed? Thanks, Tom