What Causes Constant Knocking in My Car’s Engine?

Automobile Diagnostics can determine what is causing the constant knocking in your car, truck, or utility vehicle’s engine. It’s important to figure out the cause of the knocking as soon as possible to make sure that the knocking is not damaging your engine. There is one cause of engine knocking, rod knock, that can damage the cylinder block inside the engine. Let’s talk more about this and the other causes of a knocking engine below.

Air-Filled Fuel Mixture

One thing that will make a knocking sound in your engine is multiple detonations in the cylinders. This can occur when there is more air than fuel in the mixture in the combustion chamber. The excess fuel causes the combination to ignite slowly, which can create multiple fireballs instead of just one. As these fireballs detonate, the engine makes a knocking sound.

Low-Octane Rated Fuel

The same thing can happen if you have low-octane fuel in the tank. If you drive a vehicle with a standard engine, fuel that has an octane rating of 87 is likely just fine. If you drive a high-performance vehicle, however, the manufacturer may recommend fuel with an octane rating of 91. Anything lower than this is going to fire slowly and create the multiple fireballs discussed above.

Malfunctioning Sensor

Your vehicle’s engine is equipped with a sensor that is engineered to pick up when the engine is knocking. Once it detects the knocking sounds, it notifies the engine control module of the problem so it can make adjustments. If the sensor is malfunctioning, it may not detect that the engine is knocking or it may fail to notify the engine control module of a problem.

Misfiring Spark Plugs

You may also hear knocking noises in your engine that are actually the spark plugs misfiring. This can cause multiple detonations in the cylinders. Unfortunately, if the spark plugs are misfiring, you may also end up with an engine that stalls frequently.

Worn Rod Bearings

Finally, the above causes of a knocking engine are detonation causes. We mentioned above that there is also a cause that is called rod knock. This happens when the bearings that move the rods and pistons up and down in the cylinders wear out. If they are worn, the movement inside the cylinder walls will not be smooth and the knocking that you hear is the pistons making contact with the cylinder walls.

Automobile Diagnostics in Columbus, IN, is here to help, so give us a call today if you have a problem with your car’s engine knocking.

Photo by Kritchanut from Getty Images via Canva Pro

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