Join Date: Nov 2008
Location: Salina, Kansas
Feedback Score: 0 reviews
The intake is wide open through the air filter. Engine speed is controlled by the foot feed attached to the injector pump, which will supply more or less fuel. The noise you hear sounds like (from your description) it might be an intake valve hanging slightly open, or maybe leaking. If it hangs too far it will hit the piston, but just off seat probably not.
1993 F-350 crew cab non-turbo 5 speed transmission
35 years a mechanic on large stationary engines natural gas and diesel fired, and other industrial equipment.