I’ve got a 2003 4.6L v8 f150 4x4 extended cab, it had been sitting for a while, we took it out and changed oil fuel and air filters and I’ve been driving it for a couple weeks but it tends to hard start, it normally starts ok in the morning but if I’ve been driving it for a bit and then park and try to start it it cranks for a good 15-20 seconds, it also threw the P0174 and P0171 and I’m wondering what should be the first thing to check to try and trouble shoot it, I'm used to old trucks so I’ve go very little knowledge about newer trucks

 

Can you get a code reader with freeze frame and live data capability? Freeze frame will show you what the various conditions are when the codes are set. A lean code that sets on a cold engine often has a different cause than a lean code on a hot engine.

The hard starting and the lean codes might not be related. Either way, on today's vehicles a cheap code reader/scanner can save you a lot of time and money. The concepts are the same as older engines, but the computer does much of the diagnostic work for you.

 

What is sitting for a while? Current mileage?

 

it’s got 140,000km and it was sitting for like 2 years but was taken out and started and driving a round a bit every couple months to keep the battery up and it was inside for most of the time

 

Sounds like it is cranking and trying to build fuel pressure in order to start
Test the fuel pressure
Yours is bleeding off?
Was your pump replaced some time ago?

 

pump hasn’t been replaced ever to my knowledge, I don’t really have any way to check the fuel pressure though

 

Could be something simple like a loose connection in the air inlet by the MAF sensor, or a hose popped off. Or a loose oil cap, even a dipstick, letting air in through the PCV system. Check the stuff you worked on. That's a general rule for when something bad happens after doing some work.