What causes dirty throttle and nozzle?

Hello, car owner, this is a phenomenon existing in gasoline engines. It is impossible for gasoline to burn completely. Incomplete combustion of carbon will be adsorbed at the throttle and fuel nozzle of the air intake. After a long time, carbon deposition will appear. This is usually checked once every 20,000 kilometers. If it is dirty, it can be cleaned in time. I hope my answer is helpful to you. If you have any questions, you can ask me. Have a good car. If you have any questions about cars, please ask the car master. 4S shop professional technician, 10 minutes to solve.