Q:

Why do diesel engines knock?

A:

Most knocks come from the ignition or the injector nailing. Fuel injectors can also cause a knocking noise, especially in older diesel vehicles.

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Not all knocks are harmful, so it is important to determine the cause quickly so that if there is a serious issue the vehicle owner can attend to it. Many new vehicles have mechanisms to boost pressure, adjust timing and detect knocking in the engine. One example is the Automatic Performance Control feature that is present in the turbocharged Saab H engines. This works to decrease boost pressure so that the engine no longer has a reason to knock.

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Related Questions

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    Why does my engine knock?

    A:

    Engine knock can be caused by an incorrect air/fuel mixture within one or more cylinders. The knocking sound is the fuel burning unevenly and creating shock waves at the wrong times. The waves can damage the cylinder wall as well as the piston.

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    What are Japanese engines?

    A:

    Japanese engines refer to vehicles manufactured by Japanese automobile companies that adhere to the regulations in Japan’s home market. They are also commonly known as Japanese Domestic Market cars. JDM cars might look identical to those sold overseas, but their specifications are somewhat different.

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    What does "CC" stand for in engines?

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    What causes an engine knock?

    A:

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