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
|
| • | Check the powertrain control module (PCM) grounds for being clean,
tight, and in the proper locations. Refer to
Engine Controls Schematics
. |
| • | If the scan tool readings are normal refer to supporting text
of the Diagnostic System Check--Engine Controls and there are no
engine mechanical faults, fill the fuel tank with a known
high quality fuel that meets the vehicles minimum octane requirements.
Refer to
Fuel System Specifications
. Road test the vehicle and re-evaluate the vehicles performance. |
|
Fuel System
|
| • | Check the items that can cause an engine to run lean long term
fuel trim near 24 percent. For a lean condition, refer to
DTC P0131 or P0151
. |
|
Ignition System
| Check the
spark plugs for being the proper heat range. Refer to
Spark Plug Inspection
in Engine Electrical.
|
Engine
Cooling System
| Check for obvious overheating problems:
| • | Low engine coolant--Refer to
Loss of Coolant
in Engine Cooling for the type and amount of
engine coolant to be used. |
| • | Restricted air flow to the radiator or restricted coolant flow
through the radiator. |
|
Engine
Mechanical
| Check for the following engine mechanical problems:
| • | Excessive oil in combustion chamber--Leaking valve seals.
Refer to
Oil Consumption Diagnosis
in Engine Mechanical 4.8L, 5.3L, 6.0L. |
| • | Combustion chambers for excessive carbon buildup--Clean the
combustion chamber by using top engine cleaner. Follow the instructions
on the can. |
| • | Check for incorrect basic engine parts. Inspect the following: |
|
Additional Checks
|
|
