Why is the van idle?

Idle speed adjustment method of freight cars: \x0d\ Idle speed adjustment must be carried out under normal conditions such as normal engine temperature, proper valve clearance, normal ignition system, good sealing of all pipelines, full throttle opening and tight throttle closing. When adjusting, first loosen the throttle opening adjustment screw to make the engine reach the lowest stable speed. Then screw in the idle speed adjusting screw with a screwdriver, and then slowly unscrew the idle speed adjusting screw when the engine is about to stall, so that the engine can run smoothly and reach a high speed. \x0d\ Then loosen the throttle opening adjustment screw to make the engine speed as low as possible. \x0d\ Then adjust the idle adjustment screw to increase the engine speed. Repeat this process until the throttle opening is minimum and the engine runs at the lowest stable speed. \x0d\ Finally, increase the speed and suddenly close the throttle, so that the engine can still rotate without stalling.