1999 4.7 L, Grand Cherokee.

At idle under the left valve cover you get a , rap..tap..tap..rap, sound. It will do this then quit then do it again then quit.
Pulled valve cover expecting to find deep gashes in the cover from the timing chain...nope. Inside is as smooth as the day it was made. Timing chain guide and tensioner is fine as is the chain.

When it does this you can feel the vibration through the cover as if something is hitting it.

Anyone run into this before ?

how does the engine run.....these engines are famous for dropping valve seats....is there a loose rocker?