What Causes Engine Vibration When the Car's Air Conditioning is On?

[LilahLynn]

There are several reasons why the engine may vibrate after turning on the car's air conditioning: 1. Spark plug carbon buildup: Over time, spark plugs accumulate carbon deposits. If not cleaned promptly, this can reduce the engine's torque output, leading to vibrations when the air conditioning is on. To clean, soak the spark plugs in a container of white vinegar for 2-3 hours (or 4-5 hours for severe cases), then scrub with a stiff brush to remove the carbon deposits. Rinse with gasoline, let them air dry, and they're ready to use. 2. Throttle body carbon buildup: When the air conditioning is turned on, the engine load increases suddenly, causing the throttle valve to open wider. At this point, any existing dirt or carbon buildup becomes more problematic, potentially causing the throttle valve to stick or not open to the correct position, restricting air intake and reducing engine power, which eventually leads to engine vibration. 3. Fan deformation or loose screws: Check if the vibration is caused by resonance from a deformed fan when it operates after the air conditioning is turned on, or if it's due to loose fan mounting screws causing the vibration.