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The Many Things That Make the Engine Knock

Figuratively speaking, you never want to hear a knock-knock joke from your car, truck, or C/SUV’s engine. If your engine is knocking, Ideal Automotive advises that there is a detonation or bearing problem. The engine can also sound as if it’s knocking if the accessory belt is loose and flapping around. Aside from the accessory belt, let’s talk about the many things that will make a car engine knock below.

Faulty Knock Sensor

The engine utilizes a sensor to tell the engine control module (ECM) that it is knocking. This allows the ECM to make adjustments in the combustion chamber to stop the knocking. More on this next. If the knock sensor has gone bad, it will not alert the ECM that the engine is knocking and it will continue to knock until you have the sensor replaced.

Lean Air/Fuel Mixture

One thing that the ECM does is increase the fuel in the combustion chamber if the engine is knocking due to a lean fuel mixture. This means there is more air than fuel in the mixture and this can affect your engine’s detonation. You will end up with numerous detonations in each cylinder rather than just one, and this is what makes the knocking sound.

Octane That Is Too Low

You may also inadvertently cause your engine to knock if you put the wrong gasoline in the tank. Specifically, if your car, truck, or utility vehicle requires high-octane fuel and you put low-octane fuel in the tank, the fuel will fire multiple times in the cylinders. Always make certain you have the right fuel in the tank for maximum engine performance.

Poor Engine Timing

Your engine’s timing – the spark plugs – can also cause knocking sounds. This happens if the ECM is malfunctioning and firing the plugs multiple times. The plugs can also fire out of sequence if they are old and need to be replaced. Generally, spark plugs today last 100,000 miles between changes. Have new plugs installed if you need them.

Worn Rod Bearings

Finally, the rod bearings that move the rods and pistons up and down inside the cylinders may be worn and cause a damaging knocking sound. The knock that you hear are the pistons making contact with the cylinder walls. If left unchecked, the rods may break and render your engine useless or the pistons may damage the cylinder block.

Ideal Automotive in Blaine, MN, can find the source of your engine knock and fix it. Call us today for a service appointment.

Photo by Kvisitsopa from Getty Images via Canva Pro
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