What causes the whistling sound when stepping on the accelerator that disappears upon release?
2 Answers
Stepping on the accelerator produces a whistling sound that disappears upon release, which is typically caused by air intake pipe leakage or excessive valve clearance. If there's a leak in the intake system, high-speed airflow will directly escape through the gap, not only creating a whistling noise but also reducing vehicle power. The throttle valve functions as the vehicle's accelerator, with its opening degree affecting power output. However, due to frequent opening and closing, the throttle valve wears out relatively quickly. In such cases, the only solution is to replace the throttle valve. The accelerator, also known as the "throttle" or "air valve," refers to the control device that regulates engine power (thrust). In piston aircraft engines, the throttle controls the carburetor's throttle opening to adjust cylinder filling volume, thereby determining the engine's output power.
This issue is quite common in repair shops. The whistling sound while driving is mostly related to abnormal airflow. The most likely culprit is a leak in the turbocharger's intake piping. Rubber hoses can develop small cracks or loose clamps over time, and when you step on the throttle, the boost pressure increases, causing airflow to whistle through the gaps. Another less obvious spot is the aging intake manifold gasket—a leak there can also produce a whistling sound. Also, don't overlook the vacuum hoses near the throttle body; even a small crack in a hose as thick as a pinky finger can create noise. Last time, I worked on a car where we spent half a day diagnosing it, only to find the diaphragm in the wastegate valve was torn, causing erratic airflow when accelerating. If you encounter such sounds, it's best to pop the hood, have someone press the throttle, and listen to pinpoint the source.
