What Causes the Hissing Sound When Releasing the Accelerator?

[LeAlivia]

There are several reasons for the hissing sound when releasing the accelerator: Engine Cylinder Scoring: During operation, the engine needs to intake a large amount of air. If the air is not filtered, dust particles suspended in the air can be drawn into the cylinders, accelerating wear on the piston assembly and cylinder walls. Larger particles entering between the piston and cylinder can cause severe "cylinder scoring." The air filter, installed in front of the carburetor or intake manifold, serves to remove dust and sand particles from the air, ensuring sufficient and clean air enters the cylinders. Engine Oil Deficiency: Insufficient engine oil or failure to change the oil over an extended period, leading to oil degradation, can also impair its lubricating properties, resulting in abnormal noises from component friction. If this is the issue, promptly changing the engine oil can resolve it. Additionally, damage to the car's half-shaft can cause abnormal noises when accelerating, such as twisting, breaking, or wear on the spline teeth. Furthermore, a loose engine belt can also lead to abnormal noises due to the engine revving without load.