Why does the car engine shake when the air conditioning is turned on?

[JayceRose]

When the air conditioning is turned on during normal use, the car engine shakes because the operation of the air conditioning compressor increases the engine load, causing the engine speed to drop and resulting in body vibration. Idle speed acceleration device: Most vehicles are equipped with an engine air conditioning idle speed acceleration device. When the air conditioning compressor is working, the air conditioning system simultaneously sends a command to increase the engine speed to the required range, solving the problem of engine shaking when the air conditioning is turned on. Main faults: Engine surging accompanied by shaking is a common and tricky car fault. The main reason is excessive tire inflation. Appropriately increasing the tire inflation requirement can reduce rolling resistance and save fuel when the tire is inflated.

[Diego]

When I encounter the issue of engine shaking when the car's air conditioning is turned on, I usually consider it a sign of the engine bearing additional load. When the air conditioning is activated, the compressor starts, requiring the engine to output more power to drive it. If the idle control system isn't properly adjusted, shaking occurs. Common causes include aging spark plugs leading to poor ignition, loose or worn drive belts reducing efficiency, and clogged fuel filters causing inadequate fuel supply. This is particularly noticeable in hot summers due to frequent air conditioning use. A simple check involves listening for abnormal engine sounds and observing if the idle needle fluctuates. Ignoring this issue may worsen the shaking, affecting the transmission or increasing fuel consumption, so I always recommend owners to promptly clean the throttle body or replace the air filter as a preventive measure.

[JakeLee]

As a frequent driver, I'd like to share an experience: My old car used to shake violently when the AC was turned on, and it turned out to be due to worn-out engine mounts causing loss of vibration damping. The compressor operation requires the engine to absorb vibrations, and when the mounts are worn, the vibrations are directly transmitted to the car body, making the shaking more noticeable. It could also be caused by unstable battery voltage or insufficient alternator output. In daily driving, this issue can make the ride uncomfortable, especially when the AC kicks in suddenly at high speeds. You can check this yourself by gently pressing on the hood to feel the vibration amplitude—if it's too strong, professional diagnosis is needed. Regular maintenance of these components can prevent embarrassing breakdowns on the road.

[LaQuinn]

Engine shaking when the air conditioning is on is quite common in small cars, mainly due to the increased load from the compressor causing engine discomfort. Check if the idle speed is too low or if spark plug carbon buildup is causing insufficient ignition. Insufficient tension in the drive belt can also lead to poor power transmission and cause shaking. Prolonged shaking may damage engine components. To diagnose, turn off the air conditioning and see if the engine runs smoothly for a preliminary assessment.

[GrantRose]

I feel particularly anxious when my car shakes with the AC on, as this is often caused by faults in the engine control system, such as a dirty idle control valve or sensor failure. The compressor's sudden power surge at startup can cause shaking if the engine response is insufficient. If left unresolved, it not only affects comfort but also increases fuel consumption, and even poses safety risks in congested areas. I usually recommend checking the AC system pressure before summer, ensuring proper belt tension, and timely cleaning of the fuel injection system.