Nissan Repair Questions? Ask a Mechanic for Answers ASAP
Normally if you only have a P0300 and no other codes i tend to find the problem is normally fuel related .
Fuel pressure , as this defines a misfire that is jumping around randomly .
If you don't have any.
drivability issue check the fuel pressure .
Exhaust back pressure seen bad catalytic converters cause this issue also .
Bad EGR valves .
Faulty cam / crank sensor . in some case no codes .
Vacuum leaks .do a manifold vacuum test .
Check the above and if all checks out good then please get back to me for further assistance if needed.
Kind regards Greg