For 1990-2009 cars

Cause | Correction
--- | ---
Worn or loose rocker arms | Repair or replace the valve rocker arms, as required.
Worn or bent push rods | Replace the push rods.
Sticking valves Carbon buildup on the valve stem and/or seat can cause the valve to not close properly. | Repair or replace, as required.
Excessively worn or mis-aligned timing chain | Repair or replace the timing chain, camshaft retainer, and sprockets, as required.
Worn camshaft lobes | Replace the camshaft and valve lifters.
Sticking lifters | Replace, as required.