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.
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Preliminary
Checks
|
| • | Refer to the Powertrain OBD System Check |
| • | Refer to Important Preliminary Checks Before Starting. |
| • | Refer to Visual/Physical Checks |
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Fuel System
|
| • | Check for low fuel pressure. Refer to Fuel System Pressure Test. |
| • | Check for contaminated fuel. Refer to Alcohol/Contaminants-in-Fuel
Testing. |
| • | Check items that can cause an engine to run lean (long term fuel
trim significantly in the positive range). Refer to Diagnostic Aids for DTC
P0171. |
|
Ignition System
| Check the spark plugs
for proper heat range and reach. Refer to General Information.
|
Engine Cooling System
| Check for obvious overheating
problems:
| • | Restricted air flow to radiator, or restricted water flow through
radiator. |
| • | Inoperative electric cooling fan circuit(s). Refer to Electric
Cooling Fan Diagnosis. |
| • | Correct coolant solution should be a 50/50 mix of GM 1052753
or equivalent antifreeze coolant and water. Refer to Engine Cooling.. |
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Engine Mechanical
|
| • | Excessive oil in combustion chamber-Leaking valve seals.
Refer to Engine Mechanical.
|
| • | Low cylinder compression. Refer to Engine Mechanical.
|
| • | Combustion chambers for excessive carbon buildup. Clean using
Top engine cleaner. Follow instructions on can. |
| • | For incorrect basic engine parts. Inspect the following: |
| • | Refer to Engine Mechanical.
|
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Additional Checks
|
| • | Check for proper EGR system Operation. Refer to DTC P0401 - EGR
Insufficient Flow Detected. |
| • | Check the Transaxle Range Switch input with the vehicle in drive
and the gear selector in drive or overdrive. |
| • | Check TCC operation. TCC applying too soon can cause the engine
to spark knock. Refer to Torque Converter Clutch in Transaxle Diagnosis. |
| • | If scan tool readings are normal and there are no engine mechanical
faults, fill the fuel tank with a known quality gasoline that has a minimum
octane reading of 87 and re-evaluate vehicle performance. |
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