How to detect throttle quality?

1, the engine idle speed is unstable, the high idle speed drops discontinuously, and it is difficult to start the engine, especially the cold start;

2, the engine idle speed instability or no idle speed;

3. The engine is difficult to start;

4. Insufficient engine power, poor acceleration performance and unstable operation;

5. The exhaust pipe of the car emits black smoke, which increases fuel consumption.