What Is Making My Car’s Engine Knock?

Midwest Auto Care can inspect your vehicle’s engine to determine the reason why it is knocking all the time. To play it safe, we recommend that you have your automobile towed to our shop just in case the reason why the engine is knocking is worn rod bearings. We will talk more about this below. In fact, let’s talk about all of the reasons why engines knock.

Air-Filled Fuel Mixture

Fuel and air are mixed in the combustion chamber for the spark plugs to ignite. This is what starts and maintains engine combustion. Things such as faulty oxygen or mass airflow sensors can cause the engine control module to put more air into the mixture than is necessary. This creates a lean fuel mixture that fires multiple times in each cylinder. This firing is what makes the knocking sound.

Incorrect Octane Rating

Another thing that will cause the fuel mixture to fire multiple times in each cylinder is filling your tank with gasoline that has a lower octane rating than what your manufacturer recommends for your automobile. An example of this would be to use 87 octane when the manufacturer recommends 91 octane. The lower octane does not burn as quickly and, as such, fires multiple times.

Malfunctioning Sensor

Your automobile is equipped with a knock sensor that is designed to pick up on the problems listed above and alert the engine control module. This allows the module to fix problems such as a lean fuel mixture to prevent the engine from knocking. If the knock sensor has gone bad, the engine control module will not be made aware of any problem that it can fix and the engine will knock.

Misfiring Spark Plugs

Today’s spark plugs last about 100,000 miles before they need to be changed. This sure beats changing them every 30,000 miles. If your spark plugs are too old, they will misfire and make your engine knock. Aside from the knocking sound, you may also have problems with your engine stalling.

Worn Rod Bearings

Finally, we mentioned in the introduction to this blog post that your engine could be knocking because of the rod bearings. In order for the pistons to move up and down inside the cylinders, they are attached to rods that are moved up and down by the bearings. If the bearings are worn, the pistons may be banging against the inside of the cylinder walls. This can damage the cylinder block.

Call Midwest Auto Care in Lake Station, IN, today if your car, truck, or utility vehicle’s engine is knocking all the time.

Photo by gilaxia from Getty Images Signature via Canva Pro

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