Why does my engine run rough when the AC is on?
Why does my engine run rough when the AC is on? When the engine is put under a load by the AC system, the car's computer automatically attempts to compensate for that by adjusting the idle. If there is carbon buildup within any part of the system, including the idle air control valve, throttle body, or possibly even the EGR valve, it can cause surging. What happens to the engine when the a / C is on? Hard shuttering and engine dies when A/C is on at idle. When the car is idling and the A/C is turned the engine...