What are the causes of idle air conditioning vibration?
4 Answers
The causes of idle air conditioning vibration are: 1. Intake manifold or various valve leaks; 2. Excessive carbon buildup on the throttle valve and intake passage; 3. Malfunction of the idle air actuator; 4. Inaccurate intake air volume. Idle is an operating state of a car engine, which refers to the engine speed when the car is running in neutral gear. The idle speed is adjusted by the size of the throttle valve, and the car's idle speed ranges between 600 to 800 revolutions per minute. The functions of the air conditioning system: 1. Achieve cooling effect through the continuous phase change cycle of the refrigerant; 2. Remove dust, odors, smoke, and toxic gases from the air inside the car, making the interior air fresh, and humidify the air inside the car to increase the relative humidity of the interior air.
As a veteran driver with decades of experience, I've found there are quite a few reasons for engine shaking when idling with the AC on. The AC compressor kicking in increases engine load—at low speeds, the engine is already struggling, and any instability in RPM causes vibrations. Worn engine mounts are a major issue; cracked or hardened rubber parts can't absorb the vibrations. If the idle control valve gets clogged with too much carbon buildup, it responds sluggishly and can't adjust the RPM properly. Ignition system problems are also common, such as worn spark plugs causing uneven combustion. Loose or cracked belts transmit even more shaking. My advice is to regularly monitor the engine bay's condition, inspect the mounts periodically, and clean the control valve—don't wait until the problem worsens. This shaking tends to be more noticeable in hot weather or during traffic jams, so addressing it early can save on repair costs.
Last time when I took my child out, the car shook with the air conditioning on while waiting at a red light, which worried our whole family about safety. The mechanic explained that starting the air conditioning at idle speed causes a sudden increase in engine load, leading to RPM fluctuations and body vibration; worn engine mounts lose their damping effect, transmitting vibrations directly; clogged fuel injectors in the fuel system can also worsen the shaking due to poor fuel supply; high-speed fan operation may contribute additional vibration. Remember not to leave the car idling with the air conditioning on for too long, as it may cause the generator to overheat and damage components. It's best to regularly maintain and check the support components and idle control unit to ensure safe travels for the whole family.
Having driven countless cars, I can simply explain idle AC vibration: the compressor's operation increases engine load, causing RPM to drop and natural vibration; aging rubber engine mounts are the most common cause, with failed damping; a dirty idle air control valve can't adjust RPM quickly; worn spark plugs lead to unstable combustion adding to vibration. Regular replacement of aging parts and cleaning key components can prevent most issues.
