Why does the engine shake when the car's air conditioning is turned on?
3 Answers
The reasons for engine shaking when the car's air conditioning is turned on: 1. Throttle valve carbon deposits: The most common reason for engine shaking when the air conditioning is turned on is carbon buildup on the throttle valve, which affects the engine. When the air conditioning is turned on, the engine load suddenly increases, and the throttle valve opens wider. At this point, the issue of dirt is magnified, causing the throttle valve to stick or fail to open to the proper position, restricting the air intake and reducing engine power, ultimately leading to engine shaking. 2. Spark plug carbon deposits: After a period of use, spark plugs accumulate carbon deposits. If not cleaned in time, this can reduce the engine's output torque, causing shaking when the air conditioning 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, let them air dry naturally, and they can be reused. 3. Fan deformation or loose screws: Check if the shaking is caused by resonance from a deformed fan when the air conditioning is running or by loose fan mounting screws.
When the engine shakes while the AC is on, I've seen this a lot in my ten years of driving. It's mostly due to the sudden increase in engine load when the compressor starts. If the engine mounts are worn or loose, the shaking becomes more noticeable. It could also be a vacuum hose leak, causing uneven air mixing and unstable idle speed. I always check the belt condition during maintenance because a loose or worn belt can cause the compressor to operate roughly, leading to shaking. Old spark plugs that haven't been replaced can also misfire and increase shaking. If you encounter this issue, try turning off the AC to see if the shaking stops. If it does, then the problem is likely related to AC components. Then, promptly take it to a professional shop for inspection to prevent major failures. Before long trips, ensure all engine components are in good condition to avoid this hassle.
As a car enthusiast, I've analyzed that air conditioning-induced vibrations are quite common, mainly due to the sudden increase in compressor load exposing underlying weaknesses. If engine mounts are worn out, they can't absorb vibrations effectively; vacuum system leaks can affect air-fuel mixture uniformity; loose belts may slip; and spark plug carbon buildup causing insufficient ignition can also lead to engine block vibrations. I've found that reading diagnostic trouble codes helps pinpoint issues - for instance, symptoms disappeared after replacing spark plugs. I recommend owners pay attention to maintenance schedules for these components, especially checking them before frequent summer AC use, which can save a lot of hassle.
