[danjake]

i had a similar noise. the noise occured while driving and idleing. recently had the cam sensor and synchroniser replaced and timed. i own a 99 ranger. apparently the distributor was changed by ford. the noise comes from engine up front near the cab. in my case the noise was hard to locate. an automotive place had 9+hours with no diagnosis only confusion. one first thinks the belt etc. not. removel of belt - noise got louder.
try the suggestion above. good luck