For 1990-2009 cars

#### Detonation/Spark Knock

Checks | Action
--- | ---
DEFINTION: 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 Symptoms .

• | Search for service bulletins.

Fuel System |

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

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

• | 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 .

Ignition System |

• | Check the spark plugs for proper heat range and reach. Refer to Spark Plug Visual Diagnosis in Engine Electrical.

• | Check the knock sensor (KS) system for no retard timing.

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).

• | Correct thermostat operation.

• | Correct coolant solution should be a 50/50 mix of Dexcool ® or equivalent antifreeze coolant and water. Refer to Engine Cooling.

Engine Mechanical |

• | Excessive oil in combustion chamber-Leaking valve seals. Refer to Engine Mechanical.

• | High 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:

- | Camshafts

- | Cylinder head

- | Pistons, etc.

• | Refer to the Engine Mechanical .

Additional Checks |

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

• | Check for proper operation of the MAP sensor, making sure the MAP sensor is not out of range. Refer to Manifold Absolute Pressure Sensor Output Diagnosis .

• | Check the Park/Neutral Position 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 Road Test in Automatic Transaxle.

• | If scan tool readings are normal and there are no engine mechanical malfunctions, fill the fuel tank with a known quality gasoline that has a minimum octane reading of 87 and re-evaluate vehicle performance.