GM Service Manual Online
For 1990-2009 cars only

Cause

Correction

Low oil pressure

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

Loose and/or worn follower, valve rocker arm

    • Inspect the follower, valve rocker arm.
    • Repair or replace as required.

Improper lubrication to the followers, valve rocker arms

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

    • The follower, valve rocker arm
    • The SHLA, valve lifter
    • The oil filter bypass valve
    • The oil pump and pump screen
    • The cylinder head oil galleries
    • The engine block oil galleries

Broken valve spring

Replace the valve spring.

Worn or dirty SHLAs, valve lifters

Replace the SHLAs, valve lifters.

Stretched or broken timing chain or chains and/or damaged camshaft position actuator sprocket teeth

Replace the primary timing chain, secondary timing chains, intermediate sprocket, camshaft position actuators and/or related timing components as required.

Worn timing chain tensioner or tensioners

Replace the timing chain tensioner or tensioners as required.

Worn timing chain shoe or shoes

Replace the timing chain shoe or shoes as required.

Worn timing chain guide or guides

Replace the timing chain guide or guides as required.

Worn engine camshaft lobes

    • Inspect the engine camshaft lobes.
    • Replace the camshaft or camshafts and SHLAs, 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