Need help with Volkswagen misfire codes p0300, p0303, p0301

Question

I own a 2009 Volkswagen Passat and am getting the misfire codes p0300, p0301, p0303 at different times. I've checked for a vacuum leak, replaced all spark plugs, replaced ignition coils, and replaced the air charged temperature sensor, and my check engine light is still on, and have reduced power, lost fuel economy, with high idle (rpm at 1200) and rough running upon startup. What else could be the problem, as I cannot figure it out? Any help would be greatly appreciated.

Answer 1

P0300 Random misfire

One are that very prone to cause the misfire is the crankcase breather,this is where a faulty PCV will cause pressurized intake back into the valve cover / crankcase., with the engine running disconnect the the hose from the valve cover if the idle improves replace the PCV.