Have a 2004 ford f150 5.4 , ?

Question

I am getting these three codes p0171, p303, and p0316. What would be the best thing to check first?

Answer 1

P0171 Fuel system lean bank 1

P0303 Misfire  #3 cylinder

P0316 Misfire deted during start up

The best to start first is vacuum leak, having a lean bank can cause a lean misfire on number 3 cylinder, so look for disconnected vacuum hoses,