European Auto RepairAuto Repair

My Volkswagen’s Engine Is Knocking! Why?

There are a number of reasons why your Volkswagen’s engine is knocking, and most of these reasons are related to engine detonation. Detonation is when the spark plugs light the air and fuel that is found in each cylinder. If this mixture is not detonated properly, you’ll end up with multiple detonations that make it sound as if your engine is knocking. Lucas Auto Care lists the reasons for this below.

Low Octane

Depending on the type of VW that you drive, you may be required to put gasoline in it that has a higher octane rating than 87. If you put 87 in your vehicle anyway, your engine will start to knock because you have multiple detonations going on in the cylinders. It’s important to use the octane that is recommended for your specific Volkswagen year and model.


Detonation is your engine’s timing. This is the point when the engine control module tells the spark plugs to fire. Once they do, as mentioned above, they ignite the air and fuel mixture in your VW’s cylinders. The timing can be off, and this will cause the engine to knock. The two common reasons for bad engine timing are problems with the engine control module or worn spark plugs.

Air/Fuel Mixture

Clogged fuel injectors, problems with the fuel pump, a malfunctioning mass airflow sensor, or a dead oxygen sensor can all increase the amount of air in the combustion chamber. When there is more air than fuel in the chamber, this is called a lean air/fuel mixture. This mixture does not burn quickly, and you end up with multiple detonations, i.e., knocking as a result.

Knock Sensor

Most of the time, when your engine starts to knock, the engine control module makes adjustments to correct the problem. In fact, your VW has a knock sensor that sends the message to the engine control module that there’s a knocking problem. No vehicle sensor will last forever, and this includes the knock sensor. If it’s gone bad, your engine will knock.


Your VW, or any automobile for that matter, has rods and bearings. These are the parts that help move the pistons up and down in the crankshaft. If you’ve ever broken a rod, you know that your engine is a goner. If the bearings wear down, the pistons will not go up and down uniformly, and the engine knock that you are hearing is them clanking against the crankshaft walls.

Lucas Auto Care is the best European auto repair shop in Cypress, TX. Give us a call today if your VW or other European make and model has an engine knock.

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