What Causes Engine Shaking at Idle When the AC is On?

[DelEmiliano]

Here are the reasons for engine shaking at idle when the AC is on: 1. No RPM increase with AC activation: Typically, a car's idle speed is maintained around 800 RPM. When the AC is turned on, the idle speed should normally increase accordingly, usually staying above 1000 RPM to prevent idle shaking. 2. Faulty ignition coil or spark plug breakdown: If the vehicle experiences slight hesitation during acceleration or minor idle instability without AC operation, but shows pronounced idle shaking when the AC is activated, this indicates issues with the ignition coil, spark plugs, or cylinder wires. Possible causes include cylinder misfire or incomplete combustion. 3. Excessive compressor pressure: Overly high AC system pressure increases engine load and may cause shaking. Common culprits include poor condenser heat dissipation, excessive refrigerant, or dirty AC lines - all potentially leading to excessive pressure and indirect vibration.

[Rogers]

Once when I was driving with the AC on, I noticed the idle was shaking badly, making the whole car vibrate, which was quite annoying. This is usually related to the increased load on the engine, as the AC compressor draws power when activated, making it harder to maintain a stable idle speed. There could be many reasons: aging of the engine's ignition system, like carbon buildup on the spark plugs; or clogged fuel injectors leading to insufficient air-fuel mixture; a dirty idle control valve or throttle body that can't respond quickly to load changes. Driving like this for a long time can increase fuel consumption and may be accompanied by strange noises or lack of power. Remember to perform regular maintenance, check the spark plugs and air filter, and don't wait until the shaking gets severe to fix it—sudden engine stalls on the road can be dangerous, especially in summer traffic jams. My personal habit is to clean the throttle body regularly, which can reduce the chances of shaking.

[McLilah]

When encountering the issue of engine shaking at idle with the air conditioning on, I believe it's mostly due to insufficient compensation by the engine system. The compressor requires additional power to start. If ignition components like spark plugs are worn out, weak sparks may fail to ignite; a clogged fuel injection system can lead to an imbalance in the air-fuel mixture, causing engine speed fluctuations; a dirty throttle body or idle control valve may also fail to adjust the air intake promptly. Accompanying symptoms may include unstable RPM or increased fuel consumption. It's recommended to start with simple checks such as replacing spark plugs and cleaning the air filter; use an OBD diagnostic tool to see if any fault codes indicate abnormalities in related sensors. Pay attention to whether the engine runs smoothly without the air conditioning during daily driving, as this can help detect issues early and prevent more significant damage, such as loosened engine mounts which can exacerbate the shaking.

[VanFelicity]

Oh no, car shaking with AC on? Don't panic, it's very common! When engine load increases causing unstable idle speed, shaking occurs - like the compressor greedily consuming power. Worn spark plugs or clogged fuel injectors failing to ignite timely can lead to insufficient power. You can do preliminary checks: observe if idle speed fluctuates abnormally; use a vibration recorder to document symptoms for comparison. At repair shops, a quick computer scan can pinpoint the issue - most cases just require replacing aged minor components. Regular maintenance is key - address minor shakes early before they worsen, otherwise it affects engine lifespan and may cause roadside breakdowns, impacting both mood and safety. Remember: nip small issues in the bud to avoid bigger troubles.