Symptom
| Cause
|
| • | A light tapping noise at ½ engine speed, or any varying
frequency, may indicate a valve train problem. |
| • | Tapping noises will typically increase with increased engine speed. |
| • | Before attempting to diagnose a valve train noise, check for the
proper oil level and allow the engine to obtain normal operating temperature. |
| | This will bring all engine components to a normal state of expansion. |
| • | While sitting in the driver's seat, operate the engine at various
speeds and listen for any abnormal engine noise. |
|
A light
tapping noise similar to valve train noise may be caused by the following
components:
|
| • | Evaporative emissions (EVAP) purge solenoid |
|
Valve
Train Noise
|
| • | Low engine oil pressure |
| • | A worn or faulty oil pump |
| • | A loose or plugged oil pump screen |
| • | Broken or weak valve springs |
| • | Worn or damaged valve rotators |
| • | Sticking or warped valves |
| • | Valve lifters worn, dirty, or faulty |
| • | Camshaft lobes worn or damaged |
| • | Worn or damaged valve keys |
| • | Excessive play in the camshaft timing chain |
| • | Bent, broken, or damaged timing chain sprocket teeth |
|
