What Causes the Abnormal Noise When a Car Starts?

[OAlejandro]

Abnormal noise occurs when a car starts but disappears as the speed increases. The possible causes include resonance noise and powertrain malfunction. Resonance Noise: Many parts of a car have the potential to resonate. When the car starts, the engine speed rises, resulting in higher vibrations. At this time, interior trim panels, seats, chassis, and other components may vibrate together. However, as the speed gradually increases, the engine speed stabilizes, and the vibrations decrease, causing the resonance between parts to stop, and the abnormal noise naturally disappears. In such cases, inspect each part one by one and then address the issue accordingly. Powertrain Malfunction: To quickly reach the operating temperature, the car automatically increases the idle speed. This is because most of the engine oil settles in the oil pan, and the oil's poor fluidity at low temperatures leads to inadequate engine lubrication, making it easier for abnormal noises to occur between parts. Once the engine warms up and lubrication returns to normal, this issue will resolve itself.