What Causes Engine Shaking at Idle with AC On but Not When Accelerating?

[VanGianna]

The reasons for engine shaking at idle with AC on but not when accelerating: Ignition system issues: Spark plugs have a limited lifespan. If spark plugs have been used for an extended period, they may exhibit poor sparking performance, leading to unstable idle conditions. Therefore, it's essential to promptly inspect the ignition system, including checking whether the spark plugs need replacement or if there's excessive carbon buildup. If such issues are confirmed to be causing idle shaking, immediate replacement of spark plugs or cleaning is necessary. Throttle body requires cleaning: The proper functioning of the throttle body directly affects the engine's operational stability. During vehicle operation, carbon deposits can accumulate in the throttle body. Excessive carbon buildup can obstruct normal engine air intake, resulting in insufficient engine power to adequately drive the compressor or barely managing to do so. In such cases, activating the AC at idle may cause engine shaking. Thus, it's crucial to inspect the throttle body for cleanliness and perform timely cleaning if necessary.