Q: Misfire after installing AC

Hello. In most cases the AC system should not affect the operation of the engine. If the issues only began after the AC was installed, it may be possible that the issue developed while the AC was being worked on. Perhaps a wire, hose, or sensor was damaged or disturbed during the installation. Misfires can be caused by many things, ranging from issues with the fuel system, to a faulty ignition coil, to a bad engine sensor or wiring. It could also be possible that the additional engine load placed by the installation of the AC has exasperated an already present problem. If the check engine light is on, retrieving the trouble codes will likely shed some light on what the issue could be. As engine misfires can sometimes be difficult to diagnose, if you are unsure, I would recommend having a professional technician, such as one from YourMechanic, visit your location to diagnose what may be causing the issue.