Why does the car's idle speed needle shake slightly?

[DiJames]

Reasons for slight shaking of the car's idle speed needle: leakage in the exhaust valve, loose throttle seal, abnormal spark plugs and cylinder pressure. This situation occurs when the engine is unstable in various operations, with single or multiple cylinder misfires. It is recommended to first check whether the spark plugs and throttle are working normally, and then proceed with cleaning. If high-power electrical equipment is used in the car during idle speed, turning it on or off will affect the engine's operation, causing unstable idle speed and slight shaking of the needle. The engine idle speed is not high to begin with. Using air conditioning, high-power audio systems, or external power supply will increase the burden on the engine and battery. At this time, the engine ECU will adjust the speed according to the situation to adapt to the high load.