[jhv48]

Also sounds like your throttle shaft in the base plate may be sticking or your return spring is too weak. Open the engine compartment and rev the engine by hand if the throttle doesn't snap shut when you release it, help it with your finger. If it won't return to idle immediately, then something else is going on. Throttle should snap shut and return to idle speed immediately when throttle pedal released. Could be a sticking throttle shaft in the baseplate or too weak of a return spring. Solve this one first. If you have to, disconnect the throttle cable/rod and manipulate the throttle by hand. It should open smoothly and snap shut completely when you release it.