For 1990-2009 cars

#### 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 the Powertrain On Board Diagnostic (OBD) System Check

• | Refer to Important Preliminary Checks Before Starting.

• | Refer to Visual/Physical Checks

• | Search for bulletins.

Fuel System |

• | Check for low fuel pressure. Refer to Fuel System Pressure Test .

• | Check for contaminated fuel. Refer to Alcohol/Contaminants-in-Fuel Test .

• | Check items that can cause an engine to run lean (long term fuel trim significantly in the positive range). Refer to DTC P0171 Fuel Trim System Lean .

Ignition System | Check the spark plugs for proper heat range and reach. Refer to General Information.
Engine Cooling System | Check for obvious overheating problems:

• | Low engine coolant.

• | 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.

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:

• | Camshaft

• | Cylinder heads

• | Pistons, etc.

• | Refer to Engine Mechanical.

Additional Checks |

• | Check for proper EGR system Operation. Refer to DTC P0401 Exhaust Gas Recirculation (EGR) Flow Insufficient .

• | 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.