When i start my f-150 (1999 5.4 Liter) on a cold day i have trouble starting it. It will not goe into fast idle it barely runs until it gets warm then it run normal. I also noticed that while i'm driving my lights dim when i come to a stop. then run normal while gassing . I have a EDGE computer on my truck and no codes are showing. Can anyone help me???????

 

Alternator maybe but definetely look into the battery dying. How long since it's been replaced? It also sounds like your idle air control IAC is needing a cleaning, happens a lot with cold weather.