Hello ! I recently purchased a 2006 lariat 5.4 with 173k miles. I have two codes P0171 - too lean and P0172 - too lean . Today the truck turned off twice while stopped but it starts right back up . When I turn it on the idle is rough and goes up and down and then eventually turns off . It also sometimes does not want to turn on . Any ideas on what this may be ? I’m open to anything at this point

 

The most obvious would be a vacuum leak. I would also want to check fuel pressure, fuel filter and perhaps a cleaning of the MAF sensor. Doing another scan of the computer would yield a lot of information such as fuel trims and the output of your various sensors.