For 1990-2009 cars

## Detonation/Spark Knock f

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 .

• | Refer to Visual/Physical Checks .

• | Search for bulletins.

Fuel System |

• | Check for incorrect 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 Diagnostic Aids for DTC P0171 Fuel Trim System Lean Bank 1 .

Ignition System |

• | Check the spark plugs for proper heat range. 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.

• | Electric cooling fan(s) operation. 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 TCC operation. TCC applying too soon can cause the engine to spark knock. Refer to Automatic Transmission 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.