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
|
• | Road test the vehicle and determine the severity of the complaint. |
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Cooling
System Checks
|
• | Check for any obvious overheating problems. Refer to
Engine Overheating
in Engine Cooling. |
• | Check for a low engine coolant level. Refer to
Loss of Coolant
in Engine Cooling. |
• | Check for a loose water pump belt. |
• | Check for restricted air flow through the radiator, or a restricted
coolant flow. |
• | Check for a correct coolant solution. The solution should be a
50/50 mix of anti-freeze and water. Refer to
Coolant Concentration Testing
in Engine Cooling. |
|
Sensor
Check
| Check
for an engine coolant temperature (ECT) sensor that has a shifted value.
Refer to
Temperature Versus Resistance
.
|
Fuel System Checks
|
• | 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.
Refer to
Fuel System Specifications
.
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. |
|
Ignition
System Checks
|
• | Inspect the spark plugs for excessive deposits that can glow and
pre-ignite the air/fuel mixture. Refer to
Spark Plug Inspection
. |
|
Engine
Mechanical Checks
|
• | 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. |
|
Additional
Checks
|
• | 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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