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 Powertrain On Board Diagnostic (OBD) System Check

• | Refer to Important Preliminary Checks Before Starting in Symptoms .

• | Refer to Visual/Physical checks in Symptoms .

• | Search for bulletins.

Fuel System |

• | Check the fuel pressure.

- | Refer to Fuel System Pressure Test (VIN K) .

- | Refer to Fuel System Pressure Test (VIN 1) .

• | 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. Refer to Maintenance Items .
Engine Cooling System | Check for obvious overheating problems:

• | Check for low engine coolant.

• | Check for a restricted air flow to radiator or restricted water flow through radiator.

• | Check the electric cooling fan(s) operation. Refer to Electric Cooling Fan Diagnosis .

• | Inspect for the correct coolant solution. A 50/50 mixture of ethylene glycol (Dexcool®) should be used. Refer to Coolant Concentration Testing .

Engine Mechanical |

• | Inspect for excessive oil in combustion chamber-Leaking valve seals. Refer to Oil Consumption Diagnosis .

• | Check for low cylinder compression. Refer to Cylinder Leakage Test .

• | Check 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 Overhaul

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. Refer to Functional Test .

• | Check TCC operation. A malfunctioning TCC can cause the engine to spark knock. Refer to Functional Test .

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