I been getting this code for a while already. It used to happen for a few minutes then go away. Then it got worse and stayed misfiring. It turns out the coils are still good but the plaztic stems going to the spark plugs have tiny cracks causing the charge to arc to the head.

First start the car. Then pull the plugs on the coils one at a time. If the rpm drops then thats ur problem cylinder. For the drivers side u need to pull the air tube and MAF sensor plug so the car will run with out them in place.

Also be carefull if u pull the coils cuz the plastic stems are very brittle when they get a bit old and once they develop cracks the charge will find a way out and cause arcing.

 

Great help for anyone with this code and alot of people get it i know. Definitely need to unplug the MAF sensor leave it plugged in and to the side and car will die. Found out from experience haha

 

The P0300 plagued me for a while. If i let the car sit it would misfire a bit then go away eventually. I let it go but now the misfire wont go away. Kinda sucks but I was able to narrow it down a bit. Hopefully the problem will get solved.