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 chain(s)

Replace the timing chain(s) and sprockets as required.

Worn camshaft lobes

Replace the camshaft(s) and SHLAs (valve lifters).

Sticking SHLAs (lifters)

Replace the SHLAs as required.