What are the symptoms of Jetta valve leakage?

The following are the symptoms of Jetta valve air leakage: 1, generator power is insufficient, it is difficult to start, and the exhaust gas emits black smoke. 2. When the crankshaft rotates, the resistance decreases, and the abnormal sound of "_ _" can be heard at the intake and exhaust pipes. 3. At the exhaust muffler, if you hear a "squeak" sound, it means that the engine exhaust valve is leaking; On the intake side, a "hiss" sound is heard, indicating that the engine intake valve is leaking. The following is the effect of air leakage from the valve: 1, which leads to the weakness of the vehicle. 2, resulting in incomplete combustion of fuel in the combustion chamber, resulting in increased fuel consumption. 3, resulting in slow acceleration of the car. 4. The engine is difficult to start, the power is reduced, the combustion is incomplete, the carbon deposition is serious, and even some cylinders do not work.