Engine detonation is the point at which the air and fuel in each cylinder are ignited by sparks from the spark plugs. There are certain conditions caused by specific problems that will throw the detonation off and you will end up with multiple firings in each cylinder instead of just one firing. McCurley’s Shell advises that when this happens, the multiple firings are creating the engine knock that you hear.
Bad Engine Timing
Diving into this a little deeper, the spark plugs are set to fire in a specific order. This order is controlled by your vehicle’s main computer chip, the engine control unit (ECU). If the spark plugs are dirty or worn, they may not fire in the correct order and this can cause multiple detonations in the cylinders. If the ECU is malfunctioning, it may fire the spark plugs in an incorrect order and also cause multiple detonations.
Lean Fuel Mixture
Another problem that can cause multiple detonations in the cylinders is a lean fuel mixture. This means that there is more air than fuel in the mixture found in each cylinder. In this case, the air will cause tiny fireballs to go off inside the cylinders. These detonations are the engine knock that you hear. You may have a lean fuel mixture if there is a fuel delivery problem or an issue with your MAF or O2 sensor.
Low Octane Gasoline
Gasoline that has an octane rating that is too low for your engine will also cause engine knock. Again, this goes back to the multiple firings going on inside each cylinder. Low-octane gasoline does not fire as quickly as high-octane gasoline does. Consequently, this enables it to fire more than once, which is all it should fire inside each cylinder. Check your owner’s manual for the recommended octane rating for your automobile.
Malfunctioning Sensor
Detonation knock can also be indirectly caused by a malfunctioning sensor in your engine. Specifically, your engine has a sensor that detects engine knock. If this sensor goes bad, it will not notify the ECU that the engine is knocking. This prevents the ECU from making adjustments, such as adding more fuel to the cylinders to prevent a lean fuel mixture to stop the knocking.
Worn Rod Bearings
Finally, there is one cause of engine knock that is not related to detonation. This cause is worn rod bearings. If the bearings are worn out, the rods will be unable to move the pistons up and down in the cylinders smoothly. Consequently, they will bang against the cylinder walls.
Naturally, this last cause of engine knock can severely damage your engine, so call McCurley’s Shell in Atlanta, GA, today if your engine is knocking constantly.