Why does the car idle shake after running on the highway?

[McAdriana]

The reasons for the car idling shake after running on the highway: dirty throttle body, vacuum tube leakage, excessive carbon deposits in the fuel injector. When there is too much carbon deposit inside the engine, the gasoline sprayed by the cold start injector will be largely absorbed by the carbon deposits, resulting in an overly lean mixture for cold start. In this situation, the car will only start easily after the carbon deposits have absorbed enough gasoline to reach saturation. The lower the temperature, the more fuel is required for cold start, and the presence of carbon deposits will significantly affect the smoothness of the cold start. Another reason is poor quality engine oil. Due to prolonged high-speed driving, the engine oil becomes thinner and cannot provide proper lubrication, leading to engine shaking. It is recommended that the owner replace it with a full synthetic engine oil.