loud noise on top end of motor on passenger side

What is your question?

The motor idle's ruff and has a loud clunking noise around the front of the valve cover,when its scaned at the shop it poles up 02 sencer codes...The noise does sound like it could be close to the timing chain as well,could of it jumped a notch,and if it gid jump a notch wouldnt it be noisy on every valve???