What Causes Idle Vibration When the Air Conditioner is On?
2 Answers
The main reason for idle vibration when the air conditioner is on is excessive compressor pressure. Below are the relevant explanations: 1. Throttle valve blockage: Generally, a car's idle speed is maintained at around 800 RPM. When the air conditioner is turned on, the idle speed should normally increase accordingly, usually staying above 1000 RPM to avoid idle vibration. If the idle speed vibrates when the air conditioner is on, cleaning the throttle valve and re-matching it may help. 2. Ignition coil breakdown: If the idle speed vibrates when the air conditioner is on, it indicates a fault in the ignition coil, spark plug, or cylinder wire, usually caused by the ignition coil being broken down. 3. Excessive compressor pressure: If the air conditioner pressure is too high, it increases the engine load, causing vibration. Poor condenser heat dissipation or excessive refrigerant may lead to excessive pressure, indirectly causing vibration.
After driving for so many years, I've also encountered the issue of idle shaking when the air conditioning is on, which is quite annoying. The main reason is that once the AC is turned on, the compressor kicks in, requiring the engine to exert extra effort to drive it, leading to a sudden increase in load. If the idle speed control isn't managed well—for instance, if the idle control valve responds sluggishly or there's a fault in the electronic control system—the unstable RPM can cause shaking. Worn-out spark plugs are another common factor; insufficient ignition leads to a lack of power, making the car tremble. It gets worse if the engine mounts are worn, as their poor shock absorption amplifies minor vibrations into noticeable shaking. It's advisable to regularly clean the throttle body and inspect the spark plugs. Don't skimp on maintenance to save money, as severe shaking not only affects comfort but can also be dangerous, especially during traffic jams when prolonged idling can make your hands go numb.
