GM Service Manual Online
For 1990-2009 cars only

Cause

Correction

Low oil pressure

  1. Perform an oil pressure test. Refer to Oil Pressure Diagnosis and Testing .
  2. Repair or replace, as required.

Loose and/or worn valve rocker arm attachments

  1. Inspect the valve rocker arm, bolt, and pedestal.
  2. Repair or replace, as required.

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.

Bent or damaged push rod

Inspect the following components and replace, as required:

    • The valve rocker arm
    • The valve push rod
    • The valve lifter
    • The valve lifter guide
    • The piston

Inspect the top of the pistons for valve contact. If the top of the piston shows valve contact, replace the piston and pin assembly.

Improper lubrication to the valve rocker arms

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

    • The valve rocker arm
    • The valve push rod
    • The valve lifter
    • The oil filter bypass valve
        The bypass valve is now internal to the oil filter.
    • The oil pump and pump screen
    • The engine block oil galleries

Broken valve spring

Replace the valve spring and spring shim.

Worn or dirty valve lifters

Replace the valve lifters.

Stretched or broken timing chain and/or damaged sprocket teeth

Replace the timing chain and sprockets.

Worn engine camshaft lobes

  1. Inspect the engine camshaft lobes.
  2. Replace the camshaft and valve lifters, as required.

Worn valve guides or valve stems

Inspect the following components and repair, as required:

    • The valves
    • The valve guides

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:

    • The valves
    • The valve guides