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
|
| • | Refer to Important Preliminary Checks Before Starting in
Symptoms
. |
| • | If the scan tool readings are normal (refer to supporting text
of the Powertrain On-Board Diagnostic (OBD) System Check) and there are no
engine mechanical faults, fill the fuel tank with a known high
quality fuel that meets the vehicle's minimum octane requirements. Refer
to Fuel System Specifications
.
Road test the vehicle and re-evaluate the vehicle's performance. |
|
Fuel
System
|
| • | Check for a contaminated fuel condition. Refer to Alcohol/Contaminants-in-Fuel Diagnosis
. |
|
Ignition
System
| Check
the spark plugs for being the proper heat range. Refer to
Spark Plug Visual Diagnosis
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: |
| • | Refer to Engine/Engine Mechanical. |
|
Additional
Checks
|
| • | Check the Transmission Torque Converter Clutch (TCC) operation.
The TCC applying too soon can cause the engine to spark knock. Refer to
Functional Test
in Automatic
Transmission 4L60E or
Functional Test
in Automatic Transmission 4L80E. |
|
