after replacing the timing chains on my 2001 4.6L, the engine has had a noticeable miss. after checking the circuits for the COPs and the injectors, which all checked OK, i decided to remove the valve covers. I found one of the rokcer arms on #4 cylinder lying on the head off of the adjuster/valve stem. i put the rocker back on, cranked the engine for a few seconds and it came off again. i tried to measure the valve height and it may be about an 1/8th inch short of full return. It appears i have a bent or stuck valve and that is allowing the rocker arm to fall off. Time for a valve job?

 

Might want to have this moved to the Engine forum on this site. Just PM a moderator, they'll move it for yuh.

 

The engine is an interference engine. If the valve timing is not set correctly then the piston can hit an open valve. Did you check the lash adjuster to see if it was collapsed or defective? If it is not working properly it will collapse and allow the cam follower to drop into the head.

 

The original lash adjuster was stuck in the fully extended position so i replaced it with a new one. The rocker arm continues to fall off. I'm going to pull the heads and get a valve job done.