The rubber hose from the intake to the PCV valve has a habit of collapsing and leaking. It's under and to the back of the throttle body. If it does not have a new PCV valve yet, get a motorcraft one and the hose and replace them. Make sure the return lines from the top of the valve covers to the intake tube are not cracked and that they are on. Check other vacuum lines by listening for hissing, inspection, or spraying. Sometimes pushing down on the intake will make it stop if the gaskets are bad.
