For 1990-2009 cars

Cause | Correction
--- | ---
Worn or loose followers, valve rocker arms The follower, valve rocker arm, roller bearing should be intact and in the proper position. | Replace the followers, valve rocker arms, as required.
Stuck valves Carbon buildup on the valve stem can cause the valve not to close properly. | Repair or replace as required.
Excessively worn or mis-aligned timing chains or components | Replace the primary timing chain, secondary timing chains, intermediate sprocket, camshaft position actuators and/or related timing components as required.
Worn camshaft lobes | Replace the camshaft or camshafts and SHLAs, valve lifters.
Sticking SHLAs, lifters | Replace the SHLAs as required.