low idle occasionally dtc p0171, p0300, p0442

here is an article for P0171 http://repairpal.com/OBD-II-Code-P0171-and-P0174 first that issue before you worry about the P0300 which is a random misfire, which can be caused by a lean condition which you have in a P0171. The P0442 is an EVAP System small leak, try a new FACTORY gas cap first, then is the code comes back read this article about P0442 http://repairpal.com/OBD-II-Code-P0442 ( I wrote these articles to help consumers and even shops ) I do Emissions work in CA and have dealt with this stuff for about 25+ years, and it still humbles me.