What Causes Intermittent Idle Shaking When the Car's Air Conditioner is On?

[SanFelix]

Intermittent idle shaking when the car's air conditioner is on can be caused by the following reasons: 1. Unstable oil pressure: If the fuel pump's oil supply pressure is abnormal or the intake pressure sensor's values are incorrect or malfunctioning, it can cause the car body to shake. The solution is to check the oil pressure and replace parts if necessary. 2. Excessive engine carbon deposits or aging: Excessive carbon deposits inside the engine can absorb a large amount of gasoline sprayed by the cold start injector, resulting in an overly lean mixture during cold starts and making it difficult to start. In this case, the car will only start easily once the carbon deposits have absorbed enough gasoline. After starting, the gasoline adsorbed on the carbon deposits will be sucked into the cylinder by the engine's vacuum suction force and burned, making the mixture too rich. This alternation between lean and rich combustible mixtures causes idle shaking after a cold start. The solution to this problem is to clean the fuel system and check if the idle speed motor has carbon deposits, which should be cleaned thoroughly.