Hi everyone!Could somebody help me,what's mean the check engine light PO300,and 305. Once happened,the check engine light was on,and the car got a good gas,91 at a good gas station,and after a while,a couple miles after the check engine light gone.But came up againat the next day.And the car jerking.What cause it?Water in the tank,or fuel injector problem,cylinder head gasket?Not long ago was changed the ignition coil,maybe couple months ago.
Thanks any help!

 

That's a misfire. Try watching this Don't think it's gas related, but in any case, make sure the gas tank cap is properly tighten.