Checks
| Action
|
Definition: A mild
to severe ping which is usually worse upon acceleration. The engine makes
sharp metallic knocks which change with the throttle opening.
|
Preliminary Checks
|
| • | Make sure the vehicle has an actual problem. |
| • | Check the fuel quality. Refer to Fuel Quality Diagnosis
. |
|
Cooling System Checks
|
| • | 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 proper operation 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 the Engine Coolant Temperature (ECT) sensor. Use
the Scan Tool in order to compare the engine coolant temperature with the
ambient air temperature on a cold engine. If the coolant temperature reading
is more than 5° greater or less than the ambient air temperature on a
cold engine, check for a high resistance in the coolant sensor circuit or
the sensor itself.
|
Fuel System Checks
|
Important: The mostly likely cause of a fuel related knock is a stuck closed injector
(sound is similar to a engine mechanical knock).
| • | The scan tool can be used to cut out a specific cylinder to determine
what cylinder or cylinders are affected. It may be difficult to determine
the exact cylinder the knock is coming from because cutting out a cylinder
at idle will affect the fuel charge for the nozzle next in the firing order
(both nozzles should be checked). A suspected injector can be swapped to
another cylinder to see if the knock travels with it. Refer to Injection Nozzle(s) Diagnosis
. |
| • | Check for air leaks in the fuel supply to the injection pump.
Refer to Fuel Supply System Check
. |
| • | Check the injection pump static timing. Refer to Injection Timing Adjustment
. |
| • | Check the injection nozzles. Refer to Injection Nozzle(s) Diagnosis
. |
|
Engine Mechanical Checks
|
| • | Check for incorrect basic engine parts such as the cam, the heads,
the pistons, etc. |
| • | Check for any excessive oil entering the combustion chamber. |
|
Additional Checks
| Check the Service Bulletins for control module software
updates.
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