Why does the car engine shake when the air conditioner is turned on?
2 Answers
The most common reason for engine shaking when the air conditioner is turned on is a dirty throttle body, which affects the engine. The idle shaking caused by turning on the air conditioner is different from the normal slight vibration of the engine at idle; it is a more noticeable shake. More relevant information is as follows: 1. After turning on the air conditioner, the compressor also operates, and since the compressor is driven by the engine, its operation increases the engine's load. When the air conditioner is on, the compressor works as well, and since it is driven by the engine, the compressor increases the engine's load. An increased load means the throttle opening needs to widen, allowing more air intake. 2. If the throttle body has not been maintained for a long time, carbon deposits can easily form. These deposits can obstruct the engine's air intake, making it difficult or barely sufficient for the engine to drive the compressor, resulting in idle shaking. Therefore, the throttle body needs to be cleaned. If the driving environment is harsh, it is best to clean it regularly, recommended every 10,000 kilometers.
I often encounter engine shaking when the AC is on. It's mainly because the compressor starting up increases the engine load, causing unstable idling. I have an old car where the steering wheel would shake badly when the AC was on, and later I found out it was due to severe carbon buildup in the throttle body. After cleaning it, the situation improved a lot. Common causes include: aging spark plugs, clogged air filters, or insufficient fuel pump pressure. These small issues accumulate and lead to severe shaking, especially when the compressor consumes a lot of energy during idling. I suggest first checking if the belt is loose—unusual noises can help determine this. Also, keep an eye on the coolant temperature gauge and RPM fluctuations, as excessive variations can affect safety. Regular maintenance, like cleaning the throttle body, keeps the engine running smoothly and can even reduce fuel consumption a bit. In short, don’t ignore the shaking—safety first. Head to a shop for diagnosis; it won’t take much time.
