
Originally Posted by
kevint2
If the vacuum hose to the brake booster came off the intake manifold, is cracked or broken, or if the brake booster has a bad diaphragm, it could certainly cause this condition. Not only would it cause your engine to rev up to pretty high RPMs, it would cause your brakes to function poorly and require a huge amount of effort to stop the vehicle. Look for a hose about 1/2 to 3/4 of and inch in diameter going from the intake manifold to a canister on the driver side of the engine compartment at the fire wall. Check to make sure it's connected at both ends and if it has any leaks or cracks.
This could also be caused by the throttle plate sticking open. Either due to a hung or stuck throttle cable, or mechanical damage. If the vehicle has cruise control (which I would assume it does), there is another cable involved in actuating the throttle that could be causing the problem. The cruise control stepper motor could also be stuck in one position.
There is also an item called an idle air control motor or solenoid (also known as an IAC) located near the throttle body which can often stick in position if internally, it catches "gunk" or "sludge"... Sometimes they have even been known to come apart due to wear. If it only does the revving when it's not in gear, this is a likely scenario depending on the position it may be stuck in.