Detonation/Spark Knock
Checks
| Action
|
DEFINITION: A mild to severe ping which usually occurs worse while under acceleration.
The engine makes sharp metallic knocks that change with throttle opening.
|
Preliminary Checks
|
| • | Verify that the engine control module (ECM) grounds are clean, tight,
and in the correct locations. |
| • | If the scan tool readings are normal and there are no engine mechanical
conditions, 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 the vehicle's performance. |
|
Fuel System
|
| • | Test or inspect items that can cause an engine to run lean. For a lean
condition, refer to
DTC P0171
. |
|
Sensor/System
| Use a scan tool to monitor the knock sensor (KS) system. Refer to
Knock Sensor (KS) System Description
and
DTC P0327
.
|
Ignition System
| Verify that the spark plugs are of the correct heat range. Refer to
Ignition System Specifications
.
|
Engine Cooling System
| Test for obvious overheating conditions. Test or inspect for the following conditions:
| • | Low engine coolant level |
| • | Incorrect engine coolant |
| • | Restricted air flow to the radiator or restricted coolant flow through
the radiator |
| • | Incorrect fan operation |
| | Refer to the following procedures
in Engine Cooling: |
|
Engine Mechanical
| Inspect for the following engine mechanical conditions:
| • | Excessive oil in the combustion chambers and for leaking valve seals. |
| • | Excessive carbon buildup in the combustion chambers. Clean the chambers
with top engine cleaner. Follow the instructions on the can. |
| • | Inspect the following for incorrect basic engine parts: |
| - | The pistons, connecting rods, and bearings |
| - | Refer to the following
procedures in Engine Mechanical - 2.0L (L34GMDAT): |
|
Additional Checks
| Test the transmission torque converter clutch (TCC). Applying the TCC too soon
can cause the engine to spark knock.
|
