Detonation/Spark Knock
WARNING: This page does not describe the selected car, but rather 6 other vehicles, including the 2004 Oldsmobile Bravada, 2004 GMC Envoy XUV, 2004 GMC Envoy XL, 2004 GMC Envoy, and 2004 Chevrolet TrailBlazer. However, it is still accessible from the selected car via links, so may be relevant.
Detonation/Spark Knock
| Inspections |
Action |
| DEFINITION: A mild to severe ping, usually worse under acceleration. The engine makes sharp metallic knocks that change with the throttle opening. |
| Preliminary |
|
| Cooling System |
- Inspect for a low engine coolant level.
- Inspect for a correct coolant mixture.
- Inspect for the proper tension on the drive belts. Refer to Drive Belt Tensioner Diagnosis
in Engine Mechanical.
- Inspect for restricted air flow through the radiator, or restricted coolant flow.
- Inspect for a faulty thermostat. Refer to Thermostat Diagnosis
in Engine Cooling.
|
| Sensor/System |
Inspect for an engine coolant temperature (ECT) sensor that has a shift in value. Refer to Temperature vs Resistance
. |
| Fuel System |
- Drive the vehicle at the speed of the complaint. Monitoring the fuel trim will help identify the problem.
- If the system is lean, the long term fuel trim will be more than 150.
- Test the fuel pressure. Refer to Fuel System Diagnosis
.
- Inspect for a poor fuel quality and a proper octane rating.
- If the fuel trim readings are normal and there are no engine mechanical concerns, then fill the fuel tank with a known good fuel and re-evaluate the vehicle performance.
|
| Ignition System |
- Inspect the spark plugs for their proper heat range and gap.
- Inspect the knock sensor (KS) system operation.
- Inspect the ignition timing.
|
| Engine Mechanical |
- Inspect for carbon build up. Remove the carbon with a top engine cleaner. Follow the instructions on the can.
- Test the combustion chamber pressure by performing a compression test. Refer to Engine Compression Test
in Engine Mechanical.
|
| Additional |
|