What Causes Abnormal Noise During Engine Idling?
3 Answers
Abnormal noise during engine idling may be caused by aging engine mounts. Engine Mounts: The connection points between the engine and the vehicle body typically use flexible connections, with most vehicles employing rubber engine mounts, while high-end models may use hydraulic rubber mounts. The function of engine mounts is to absorb vibrations generated by the engine, preventing them from being transmitted to the vehicle body. Replacing Engine Mounts: Simply replace the aged engine mounts. Although replacing engine mounts is a straightforward process, it can be quite time-consuming, so it is recommended to have it done at a 4S shop. After installing new engine mounts, it's also important to check whether vibrations continue to occur in the cabin during driving.
I've repaired many cars, and the most common cause of abnormal engine idle noise is belt issues—a loose or aged/worn belt can produce squeaking or rumbling sounds, especially noticeable during cold starts. It could also be a faulty bearing component, such as worn bearings in the water pump, alternator, or tensioner pulley, leading to a continuous humming noise. Faulty spark plugs or ignition coils may cause a tapping sound, particularly when fuel combustion is incomplete. Hydraulic lifter failure is also common in the valve train. These sounds may seem minor, but ignoring them can lead to major problems, such as internal engine component damage. I recommend immediately checking belt tension and bearing condition, trying lubrication first, and if that doesn’t help, seeking professional repair early to avoid compromising driving safety. Regular maintenance should include monitoring these parts and replacing belts and bearings periodically to prevent future issues.
When encountering abnormal engine idle noise, I recall that experience: the rattling sound in my car turned out to be caused by a loose timing chain, and it became quiet after replacement. Sometimes insufficient belt tension or aging wear can also cause trouble, with annoying squeaking sounds. A failed bearing, such as the alternator bearing, can cause a humming noise, while ignition system failures like spark plug issues may result in popping sounds. Hydraulic lifters failing or loose engine mounts are also common culprits. Never ignore these abnormal noises; address them promptly to prevent severe engine damage. It's recommended to first check the belt yourself to ensure it's neither loose nor cracked. If the situation seems bad, take it to a repair shop for diagnosis. Regular maintenance is key—check the belt and bearing condition monthly to extend your car's lifespan and ensure a safe driving experience.
