First time post. I have a 03 F150 with the 5.4 Triton. Since the weather has been cold I have had trouble starting when the truck sits for more than 3 or 4 hours without running. On warmer days it can sit longer before I have trouble. It will turn over but then die right away. If I give it a lot of gas and get the RPM's up i will hear it catch and I won't have any other problem. Any ideas what this could be?

Also in the last few months I've changed the IAC because the truck was actually dieing at stop signs and red lights which solved that problem. I've also had to put in a new gas tank due to a leak. While doing that we switched out the fuel tank pressure sensor and the fuel filter, and then checked the fuel pump which seemed to be in good working order. I've also put in a new alternator, battery, brake pads, and rotors (which I know has nothing to do with this problem).

 

How does it do under heavy load / acceleration / uphill? Any stored codes?

 

I had a P1450 code (fuel tank unable to bleed) which is why we switched out the fuel tank pressure sensor. Also checked for kinked lines and didn't find anything. Code hasn't came back.

I've noticed a little struggle going uphill and accelerating.

 

Tank unable to bleed may be a bad fuel cap. Is there a bunch of pressure when you remove it ?

 

Forgot to mention I changed the fuel cap as well. Check engine light hasn't came back on since changing Fuel Tank Pressure sensor a week ago. Just having trouble cold starting after it's sat awhile.

 

So it runs fine after start ? Check the regulator next.

 

After I get it started it runs fine for the most part. It idles a little rough for a few moments but after a minute or so it is ok. I feel like its lost a little power on hills but that could also just being my mind playing tricks on me waiting for something bad to happen.

I've checked all my fuel lines and changed fuel filters now as well. Still having the same issue in the mornings and after work.