on failure codes p0300 random misfires, the cause of those are many. first to consider is weak secondary spark plug voltage, ie. coil,spark plug cable, spark plug. if vehicle has not had a tune-up done. then consider a complete tune-up replacing spark plugs and spark plug wires first.the other to consideer is fuel injector maintenance, also if it hasn't been done in a while could be cause of problem. fuel injector cleaner "TECHRON" chevron brand works best from my past experiences, also direct fuel injector cleaning by a fuel injector cleaning machine works, last and very hard to find would be an intake manifold lleak, this would be found esier using a stetoscope with a small funnel at the end so you can hear the vacuum leak a lot easier, don't forget to check all the vacuum hoses too.