I have a 1999 ford taurus and codes 171,174, 300?

Question

I have a 1999 Ford Taurus with a rough idle and codes PO171,PO 174 and PO 300.

Answer 1

P0171 Fuel trim lean Bank 1

P0174 Fuel trim lean Bank 2

P0300 Randim misfire

False air ir vacuum leak is what causes the engine to get a random misfire, what false air or vacuum leak is air that gets past the MAF (Mass air flow) you can probably hear the vacuum leak with the engine at idle, this can be the PCV valve or ruptured vacuum hose.