Low oil pressure.

Perform an oil pressure test. Refer to Oil Pressure Diagnosis and Testing.

Loose and/or worn valve rocker arm attachments.

1. Inspect the valve rocker arm, bolt, and pedestal.
2. Replace the valve rocker arms, as required. Refer to Valve Rocker Arm and Push Rod Replacement.

Worn or damaged valve rocker arm.

1. Inspect the rocker arm for wear or missing needle bearings
2. Replace the valve rocker arms, as required. Refer to Valve Rocker Arm and Push Rod Replacement.

Bent or damaged push rod.

Inspect the following components and replace, as required:

Incorrect lubrication to the valve rocker arms.

Inspect the following components and repair or replace, as required:

Broken valve spring.

Replace the valve spring and spring shim. Refer to Valve Stem Oil Seal and Valve Spring Replacement.

Worn or dirty valve lifters.

Replace the valve lifters. Refer to Valve Lifter Replacement.

Active fuel management valve lifter with a broken spring.

Replace the valve lifters. Refer to Valve Lifter Replacement.

Incorrect operation of the active fuel management oil pressure relief valve.

Repair, as required. Refer to Cylinder Deactivation (Active Fuel Management) Oil Pressure Relief Valve Diagnosis and Testing.

Stretched or broken timing chain and/or damaged sprocket teeth.

Replace the timing chain and sprockets. Refer to Camshaft Timing Chain and Sprocket Replacement.

Worn engine camshaft lobes.

1. Inspect the engine camshaft lobes.
2. Replace the camshaft and valve lifters, as required. Refer to Camshaft Replacement.

Worn valve guides or valve stems.

Inspect the following components and repair, as required:

Stuck valves.

Carbon on the valve stem or valve seat may cause the valve to stay open.

Inspect the following components and repair, as required: