Diagnosing Noises From Your Car

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Most of us love our vehicles, especially more so when the noises that it makes are pleasant and natural. However, in some cases you could hear a noise that definitely shouldn’t be coming from your vehicle, anywhere from your valve train to the fuel in your car can cause these noises, and I am going to share with you some tips as to what could be causing your baby to be making these noises.

Valvetrain Noise

Valve and tappet noise usually begins as a clicking sound, or chatter, at half engine speed and may then disappear at high speeds. The cause is often excessive valve clearance or a defective hydraulic valve lifter.

Piston Pin Noise

Although similar to valvetrain noise, piston pin noise often has a unique, metallic-sounding double knock and is sometimes most noticeable during idle with the spark advanced. This noise is often caused by a worn or loose piston pin, worn bushing, or lack of oil.

Detonation

Detonation can cause serious damage to an engine. This condition shows up as a knocking or metallic “pinging” sound and is most commonly attributed to improper ignition timing, lean air/fuel ratio, or improper fuel octane level. A somewhat common phenomenon in forced induction applications, detonation can be prevented by upping the octane level of your fuel, enriching the air/fuel mixture, reducing manifold pressure, or retarding the ignition timing.

Connecting Rod Noise

If you hear a light knocking or pounding sound, the noise can usually be traced back to your connecting rods. This sound is often most noticeable when the engine is at an even rpm–not accelerating or decelerating–and is often caused by a worn bearing or crankpin, misaligned connecting rod, or lack of oil.

You can single out the faulty connecting rod by performing a cylinder-balance test. This test basically shorts out the spark plugs one cylinder at a time with the engine running. Eventually, you’ll zero in on the ailing connecting rod because the noise will be reduced when its home cylinder is not delivering power.

Piston Pin Noise

Although similar to valvetrain noise, piston pin noise often has a unique, metallic-sounding double knock and is sometimes most noticeable during idle with the spark advanced. This noise is often caused by a worn or loose piston pin, worn bushing, or lack of oil.

As with connecting rod noise, you can find the offending components by performing the cylinder-balance test outlined above.

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