Why Is My Car’s Engine Knocking?

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You’re driving along and your engine starts knocking. This can be a scary sound because you don’t know what’s going on underneath the hood. It’s important to get the source of the knock investigated and fixed as soon as possible to prevent further engine damage. Accurate Auto would be happy to determine why your vehicle’s engine is knocking. In the meantime, here are three reasons why the motor could be making the annoying sound.

Spark Plugs

If you have over 30,000 miles on your automobile and you’ve never had the spark plugs changed, this could be why the engine is knocking. If your spark plugs are faulty or worn, they could be causing your engine to knock because the cylinders are misfiring. Basically, your ignition system mixes air and gas and then delivers it to the spark plugs where they generate a spark to ignite the solution. Old, worn, or the plugs other than those recommended by your vehicle’s manufacturer can make your engine knock.


We all need to save money where we can these days but if you’re saving it at the gas station by purchasing low-octane fuel, you could be the cause of your engine knocks. Pull out your owner’s manual to see which octane is recommended for your car, truck, or SUV. If it’s 89 and you’re putting 87 in the tank, your engine will knock. Always make certain you put the right octane in your vehicle to avoid engine trouble and prolong the life of your engine. If your vehicle is okay with 87, you can upgrade to higher octane if you like but you should never downgrade, as this causes engine noise.

Carbon Deposits

Carbon is a natural deposit left in your engine by gasoline and even though fuel in the U.S. contains carbon detergents, you still get deposits in your cylinders. If these deposits have built up over time, your engine might knock. The good news is you can have your cylinders professionally cleaned to remove the carbon buildup and alleviate the engine knocking. Carbon can build up in your engine every 100 hours you drive it, so this is something that you should have checked regularly and cleaned when necessary.

Is your engine knocking? Call Accurate Auto to set up an appointment for an engine inspection. We have three shops in Oregon, Beaverton, Oswego, and Hillsboro, and you call the one closest to you.