What's the noise of idling air leakage?

The reasons for the air leakage sound at idle speed are: 1, the spark plug is not easy to use; 2. The vacuum tube leaks; 3, high-voltage line leakage; 4. The 4.PCV valve is blocked; 5. The throttle position sensor is faulty; 6, stepper motor idling fault; 7, idle speed control valve failure; 8. Abnormal throttle opening; 9. Air leakage in the air intake system. There are several reasons for air leakage of the valve: 1, wear: the working inclined plane of the valve and the valve seat is worn, resulting in spots or depressions due to ablation and carbon deposition. 2. Tight closing: the gap between the valve stem and the valve guide sleeve is too large, which makes the valve stem shake and make the valve close too loosely, or the valve stem bends and deforms, which makes the valve head skew and make the valve close too loosely, resulting in air leakage.