Car Makes Noise When Releasing the Accelerator?
3 Answers
The reasons for abnormal noise when releasing the accelerator: excessive clearance in the drive shaft or poor lubrication, which should be repaired at a maintenance shop promptly. More information about the drive shaft is as follows: 1. The drive shaft consists of a shaft tube, telescopic sleeve, and universal joint. The drive shaft (DriveShaft) connects or assembles various components and is a movable or rotatable circular object accessory, generally made of lightweight and torsion-resistant alloy steel pipe. 2. The drive shaft is a high-speed, low-support rotating body, making dynamic balance crucial. Generally, drive shafts undergo dynamic balance testing before leaving the factory and are adjusted on a balancing machine.
Last time when I released the throttle while driving, there was a buzzing sound. After inspection at the repair shop, it was found that the CV joint boot was worn out. The mechanic said this kind of clicking noise is usually more noticeable when turning, especially in older cars over 5 years old. It was recommended to check if the axle seal is leaking, as dried-up grease can cause metal parts to grind dry. Also, aging exhaust pipe gaskets can produce a metal flapping sound when releasing the throttle—applying soapy water at the joints can reveal bubbles. The most concerning issue is wear on the transmission output shaft bearing; when releasing the throttle, increased gear backlash can cause a clattering sound, which needs immediate repair to avoid transmission failure.
I also encountered a similar situation after modifying the exhaust system, with loud popping sounds from the exhaust pipe when releasing the throttle. The mechanic said it was mainly caused by sudden backpressure changes: the stock blow-off valve couldn't keep up with the backpressure variations of the modified exhaust, leading to unburned fuel-air mixture igniting in the exhaust pipe during throttle release. Another possibility is loose exhaust manifold bolts, causing friction noises due to thermal expansion and contraction. It's recommended to first check the oxygen sensor data stream, as long-term overly rich fuel mixture can accelerate exhaust pipe corrosion. For some turbocharged cars, this kind of hissing sound might actually be caused by a deformed wastegate actuator rod - you can feel obvious play when manually shaking the turbo actuator rod.
