What are the symptoms of gas car accelerator failure?

When the throttle valve of a natural gas vehicle is broken, the following symptoms will appear: 1, the engine idle speed is unstable, the high idle speed continues to drop, 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.