[Roger Bray]

Hi all,
I hope this is the correct place to post this question.
I recently bought an '02 f250 with a 5.4l gas engine and I'm having a misfire issue

When the air temp is about 70 or below the truck runs like a champ.
However, when it gets hot outside I have a misfire.
The engine misfires at idle or when I'm running along at about 50mph and try to accelerate it starts to buck. It seems the hotter the outside temp the worse the problem is. I never get a check engine light.
Today the air temp is about 70 and I took the truck for a 20 mile ride and it ran without a single misfire.

Any help would be appreciated.
Roger