What Causes Car Vibration When Turning on the AC?

[DelPenelope]

Car vibration when turning on the AC is generally caused by carbon buildup on spark plugs, carbon buildup on the throttle body, or fan deformation or loose screws. Here is a detailed explanation of the reasons for car vibration when turning on the AC: 1. Carbon buildup on spark plugs: After a period of use, spark plugs will accumulate carbon deposits. If not cleaned in time, this can reduce the engine's torque output, leading to vibration when the AC is turned on. Soak the spark plugs in a container with white vinegar for 2-3 hours (or 4-5 hours for severe cases), then use a stiff brush to remove the carbon deposits. Clean them with gasoline and let them air dry naturally. 2. Carbon buildup on the throttle body: When the AC is turned on, the engine load increases suddenly, and the throttle opening expands. At this point, the issue of dirt becomes more pronounced. If the throttle is stuck or fails to open to the proper position, the air intake is restricted, reducing engine power and eventually causing engine vibration. 3. Fan deformation or loose screws: Check if the vibration is caused by resonance when the fan operates after the AC is turned on or if it is due to loose fan mounting screws.