For 1990-2009 cars

Cause | Correction
--- | ---
Worn or loose rocker arms. The rocker arm bearing end caps and/or needle bearings should be intact within the rocker arm assembly. | Replace the valve rocker arms, as required. Refer to Base Engine Misfire with Abnormal Valve Train Noise.
Worn or bent pushrods. | Replace the pushrods, as required. Refer to Valve Rocker Arm and Push Rod Replacement.
Stuck valves. Carbon buildup on the valve stem can cause the valve not to close correctly. | Repair or replace, as required. Refer to Cylinder Head Disassemble.
A worn or mis-aligned timing chain above acceptable tolerances. | Replace the timing chain and sprockets, as required. Refer to Cylinder Head Disassemble.
Worn camshaft lobes | Replace the camshaft and valve lifters. Refer to Camshaft Replacement.
Sticking lifters | Replace the camshaft and valve lifters. Refer to Camshaft Replacement.