The 4-meter-2 car is in gear, with grinding sound and high belt speed.

In some cars, the engine silencing system is incomplete and loud, but the gear shift is largely caused by the gearbox. Of course, the smoldering of the engine will also have a lot of noise, and the whole transmission system will also have irregular vibration and noise because of the difficulty of the transmission structure.

The sound reason of high engine idle speed is: 1. When the engine water temperature is low, the air conditioner is turned on, and the engine voltage is low, ECU programming should appropriately increase the idle speed. Under this normal condition, if the engine water temperature is normal and the engine idle speed is high without air conditioning, it indicates that the system is faulty, which may be an electronic control system or a mechanical system. 2. If the idle speed is too high due to mechanical failure, be sure to check whether the intake pipe leaks, whether the vacuum pipe falls off and whether the intake pipe is damaged (the intake manifold of Volkswagen engine is mostly rubber pipe). Because the air intake of the engine is very small at idle speed, if there is air leakage, it will cause high idle speed. 3. After cleaning the throttle body and idle speed control valve, the engine may have a high idle speed after starting, which requires a learning process for the computer. Because the engine idle speed will decrease after the throttle body and idle speed control valve are dirty, in order to stabilize idle speed, ECU will control the opening of idle speed control valve or throttle valve to increase the intake air, thus stabilizing idle speed. 4. After cleaning, the ECU also controls the air intake according to the original opening, and the engine idle speed will increase.