What Causes the Abnormal Noise When Releasing the Accelerator Pedal in a Car?
2 Answers
The causes of abnormal noise when releasing the accelerator pedal in a car are as follows: 1. Issues with the valve train: Generally, the noise comes from the valve train. This is because the poor fluidity of the engine oil prevents the tappet from compensating for the clearance, resulting in the noise. When the engine warms up and the oil viscosity decreases, the noise disappears as the tappet starts functioning properly. 2. Carbon contamination: Severe carbon contamination can lead to engine knocking sounds. Another possibility is noise from the hydraulic tappets in the engine's valve train, which can be resolved by replacing the affected parts. 3. Other issues: Excessive valve clearance, excessive clearance between the tappet and its guide hole, worn cam profiles, excessive clearance between the valve stem and its guide, or stuck valves that fail to close can all be sources of the abnormal noise when releasing the accelerator. It's essential to identify the root cause of the noise, whether it originates from the engine compartment or elsewhere. For instance, in some rear-wheel-drive models, releasing the accelerator can also cause gear noise. Regardless of the cause, it's advisable to have the car inspected at a 4S shop or a professional auto repair facility.
As a mechanic who frequently deals with similar issues, abnormal noises when releasing the throttle in a car can stem from multiple component failures. Common causes include the drivetrain, such as worn gears in the transmission or problems with the torque converter, which produce a clunking sound when the throttle is released due to changes in force; or the engine belt system, where an aging tensioner or cracked belt causes squealing due to slipping. I once repaired a car that made noise when the throttle was released—after extensive troubleshooting, it turned out to be loose exhaust pipe hanger screws vibrating and causing the sound. Rusted exhaust joints are also prone to producing friction noises when backpressure occurs upon throttle release. If you hear abnormal noises, don’t delay—visit a professional shop for diagnosis as soon as possible, especially noting the sound characteristics—is it a friction sound or metal collision? This can help technicians pinpoint the issue faster and avoid safety hazards. Regular maintenance checks on wear-prone parts can save both money and hassle in the long run.
