Rough Idle When AC Is On

If your engine starts shaking or the RPMs dip when you turn on the AC, the engine is struggling with the extra load.

The AC compressor puts a significant load on the engine — several horsepower worth. A healthy engine compensates by bumping up idle speed slightly when the AC kicks in. If the idle air control valve, electronic throttle body, or engine computer isn't making that adjustment, the extra load drags the RPMs down and the engine runs rough. This is especially noticeable on smaller four-cylinder engines.

Other contributing factors include a worn AC compressor that's seizing intermittently, creating uneven load spikes, or a serpentine belt that's slipping under the extra strain. Low refrigerant can cause the compressor to cycle on and off rapidly, creating a rhythmic surging at idle. Dirty fuel injectors or worn spark plugs that are barely adequate for normal idle may push the engine over the edge when AC load is added.

In Jacksonville, you're running the AC nine months out of the year, so this isn't a problem you can ignore. Ez Mobile Mechanic is a mobile mechanic in Jacksonville who diagnoses and repairs AC-related idle issues at your location. No need to drive to a shop sweating in traffic. We come to you anywhere in Northeast Florida. Call (904) 788-7272.