Detonation/Spark Knock
Checks
| Action
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DEFINITION: A mild to severe ping, usually worse under acceleration. The engine makes sharp metallic knocks that change with throttle opening.
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Preliminary Checks
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• | Road test the vehicle and determine the severity of the complaint. |
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Cooling System Checks
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• | Check for a loose water pump belt. |
• | Check for restricted air flow through the radiator, or a restricted coolant flow. |
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Sensor Check
| Check for an engine coolant temperature (ECT) sensor that has a shifted value. Refer to
Temperature Versus Resistance
.
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Fuel System Checks
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• | Check to determine if a lean system causes the condition. 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 20 percent. |
• | Check for inferior quality fuel and the proper octane rating. Fill the fuel tank with a known high quality fuel that meets the vehicles minimum octane requirements. Road test the vehicle and re-evaluate the vehicle performance. |
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Ignition System Checks
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• | Inspect the spark plugs for excessive deposits that can glow and pre-ignite the air/fuel mixture. Refer to
Spark Plug Inspection
. |
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Engine Mechanical Checks
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• | Check for carbon buildup. Remove the carbon with a top engine cleaner product. Follow the manufacturer instructions on the container. |
• | Check for incorrect basic engine parts such as the cam, the heads, the pistons, etc. |
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Additional Checks
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• | Check for a dirty air filter or a restriction in the air induction system. |
• | Check for any Service Bulletins or updates. |
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