What Causes Car Jerking When the AC is Turned On?
3 Answers
Car jerking when the AC is turned on may be caused by severe carbon buildup in the engine cylinders. Fuel supply malfunction: Engine logic error: Unable to receive the AC activation signal. When the system cannot determine whether the AC is turned on, the Engine Control Unit (ECU) mistakenly interprets it as a temporary high load and attempts to compensate by increasing the RPM to offset idle resistance. When the engine RPM drops, it cannot handle the load from the AC compressor, causing the RPM to rise again. This back-and-forth results in unstable idling. AC control circuit malfunction: Unable to send the AC activation signal. Similar to the first scenario, since the system cannot determine the AC's operational status, the ECU continuously adjusts the idle RPM, leading to unstable idling.
I often encounter this issue when driving my old car—whenever I turn on the AC, the car feels like it's being dragged and jerks constantly. The main reason is that after the AC compressor kicks in, the engine suddenly bears extra load, and if the power can't keep up, it easily causes jerking, especially in small-displacement cars or when climbing hills. Other possible factors include the compressor itself malfunctioning, such as internal wear or unstable oil pressure; or the AC system's belt being loose, causing slippage that leads to fluctuating engine RPMs. It could also be due to aging spark plugs or ignition coils failing to ignite properly, resulting in power loss. If you feel jerking when turning on the AC, it's best to check these components promptly. During routine maintenance, don’t forget to clean the AC filter and replace the belt—this can significantly reduce such issues. AC-induced jerking not only affects driving comfort but also burns more fuel, so don’t ignore it. Get a professional diagnosis to prevent minor issues from turning into major troubles.
Having driven for decades, I've seen plenty of cases where older cars jerk when the AC is turned on. When you switch on the AC, the compressor kicks in—it's like a little monster that saps some of the engine's power. Especially in traffic, when the power can't keep up, it often leads to jerking. Common causes might include a loose belt pulley causing unstable operation, unstable generator voltage leading to erratic power distribution to the AC system, or carbon buildup in the fuel injectors causing uneven fuel supply. Don’t underestimate this issue—it’s not just uncomfortable to drive, but it might also hint at more serious problems, like a failing AC compressor or electrical issues. Addressing it early saves money and ensures safety. Regular use of fuel system cleaners to maintain lubrication can keep your car running smoothly. Don’t let small issues turn into big ones.
