Q: P300 reading, loss of power, and misfiring cylinder

Code P0300 indicates there is a random misfire which can be happening in one or more of the cylinders in your Nissan. If you have a specific cylinder misfiring there is usually another code along with the random misfire code, to indicate which cylinder needs investigation. P0301 would indicate a misfire in cylinder number one, P0302 a misfire in cylinder number two and so on. Your Pathfinder also uses a coil on plug ignition system, which means each individual cylinder has its own ignition coil that provides spark to that particular cylinders spark plug. It is possible your Pathfinder will just need its’ spark plugs replaced, however there may also be issues with one or more of the ignition coils as well. To determine exactly what’s going on with your Nissan, I recommend having a certified mechanic examine the vehicle in person to give a proper diagnosis of your car’s misfiring issue.