Why does the car shake and have unstable idle speed when the air conditioner is turned on?
2 Answers
Unstable idle speed and shaking when the air conditioner is on can be caused by carbon deposits, high pressure, and other reasons. Throttle Body: Severe carbon deposits in the throttle body can block the normal air intake of the engine. Insufficient engine power makes it difficult to drive the compressor, or it can only barely do so. When the air conditioner is turned on, the engine load increases, and the throttle opening expands. At this point, the issue of dirt is magnified, causing the throttle to stick or fail to open to the appropriate position, resulting in restricted air intake. Compressor: If the compressor pressure is too high, the increased engine load will affect the car's stability. Solution: Regularly clean the throttle body and carbon deposits in the engine to avoid high compressor pressure.
I encountered this issue when driving an old car - the vehicle would shake like a sieve when the AC was turned on. The compressor draws a significant amount of power when starting up, forcing the aging engine to work harder. If the throttle body has carbon buildup at this point, insufficient air intake can cause the engine to choke and shake. I once disassembled and cleaned the throttle body myself; removing those black, greasy deposits improved the situation noticeably. A sticking idle air control valve can also disrupt RPM stability - it's best to have a repair shop inspect it. Additionally, worn-out spark plugs or faulty ignition coils causing a misfire in one cylinder will naturally make the engine shake violently. A long-unchanged air filter or fuel system contamination could also be contributing factors. If you notice these symptoms, don't force the car to keep running - find a place to get it checked to avoid breaking down midway.
