Detonation/Spark Knock
Checks
| Action
|
DEFINITION: A mild to severe ping, usually worse under acceleration. The engine
makes sharp metallic knocks that change with throttle opening.
|
Preliminary Checks
|
| • | Road test the vehicle and determine the severity of the complaint. |
|
Cooling System Checks
|
| • | Check for any obvious overheating problems. |
| • | Check for a low engine coolant level. |
| • | Check for a loose water pump belt. |
| • | Check for restricted air flow through the radiator, or restricted coolant
flow. |
| • | Check for a faulty or incorrect thermostat. |
| • | Check for a correct coolant solution. The solution should be a 50/50 mix
of anti-freeze and water. |
|
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 greater than 20%. |
| • | 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
vehicle's minimum octane requirements. Road test the vehicle and re-evaluate vehicle
performance. |
|
Ignition System Checks
| Check the spark plugs for the proper heat range and gap.
|
Engine Mechanical Checks
|
| • | Check for carbon buildup. Remove the carbon with a top engine cleaner.
Follow the instructions on the can. |
| • | Check for incorrect basic engine parts such as cam, heads, pistons, etc.
Refer to Engine Mechanical. |
| • | Check for excessive oil entering the combustion chamber. |
|
Additional Checks
|
| • | Check for the proper operation of the air induction system. |
| • | Check for any Service Bulletins or updates. |
|
