Symptoms of a broken one-way valve in a car

Difficulty in starting the engine, engine shaking, unstable idle speed, weak acceleration, substandard emissions, engine fault light on, etc. If the one-way valve is always open, it will cause the car to emit black smoke and increase fuel consumption; if the one-way valve is always closed, it will affect the car's exhaust emissions and it is very likely that it will not pass the annual inspection.