What Causes Sudden Strong Vibration When the Car Air Conditioner is Turned On?
2 Answers
There are several reasons why a car may experience sudden strong vibration when the air conditioner is turned on: 1. Dirty throttle body: If the throttle body is dirty, turning on the air conditioner can increase the engine idle load, leading to steering wheel vibration. 2. Poor fuel quality: Low-quality fuel can impair engine performance, causing idle vibration issues. 3. Ignition system problems: Faults in the car's ignition system can result in poor ignition performance and weak spark plug firing, leading to unstable conditions such as vibration during idle. 4. Excessive engine carbon buildup: If there is too much carbon buildup inside the engine, the fuel injected by the injectors during a cold start can be largely absorbed by the carbon deposits, resulting in a lean air-fuel mixture during cold starts, making it difficult to start and causing idle vibration after a cold start.
Last time I talked to the mechanic at the repair shop about this issue, he said it’s most likely caused by a compressor problem. When the compressor starts, the sudden increase in engine load can cause severe shaking. Additionally, worn-out engine mounts can have the same effect, as the hardened rubber loses its cushioning ability. A less common reason is a loose or broken drive belt, causing the pulley to slip and shake continuously. My friend’s old car once had a seized compressor, and the vibration was so bad it felt like a tractor—only replacing the entire compressor fixed it. During regular maintenance, make sure the cabin air filter isn’t clogged, as a non-functional fan can also lead to insufficient condenser cooling. If the shaking is severe, get it checked immediately; otherwise, prolonged neglect can damage the crankshaft and connecting rods.
