Worn or loose valve rocker arms

The rocker arm needle bearings should be intact within the rocker arm assembly.

Replace the 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 chain

Replace the timing chain and sprockets as required.

Worn camshaft lobes

Replace the camshaft, valve lash adjusters, and rocker arms.

Sticking valve lash adjusters

Replace as required.