Low oil pressure.

1. Verify oil pressure. Refer to Oil Pressure Diagnosis and Testing .
2. Repair or replace damaged components as required.

Improper lubrication of the valve train components.

1. Verify oil pressure. Refer to Oil Pressure Diagnosis and Testing .
2. Inspect the valve lifters.
3. Inspect the oil filter bypass valve.
4. Inspect the oil pump and pump screen.
5. Inspect the engine block oil galleries.
6. Repair or replace damaged components as required.

Broken valve spring.

1. Inspect the valve springs.
2. Repair or replace damaged components as required.

Worn, damaged or stuck valves, carbon on the valve stem or valve seat.

1. Inspect the valves.
2. Inspect the valve guides.
3. Repair or replace damaged components as required.

Worn or damaged valve guide.

1. Inspect the valve guides.
2. Inspect the valves.
3. Repair or replace damaged components as required.

Worn, damaged or dirty valve lifter.

1. Inspect the valve lifters.
2. Repair or replace damaged components as required.

Worn or damaged camshaft lobes.

1. Inspect the engine camshaft lobes.
2. Repair or replace damaged components as required.

Worn, damaged, improperly installed or loose timing belt and sprockets.

1. Inspect the timing belt and sprockets.
2. Repair or replace damaged components as required.

Worn, damaged or improperly installed timing belt tensioner, if equipped.

1. Inspect the timing belt tensioner.
2. Repair or replace damaged components as required.