A vacuum leak will cause the idle to be too high and make the engine surge. I've had a loose vacuum hose fall off once or twice and that is what happens. Reconnect and everything is fine.
Lift the hood with the engine running and listen for air leaks (if a hose is off it's easy to hear).
Lift the hood with the engine running and listen for air leaks (if a hose is off it's easy to hear).
