f250 misfires when air temp is hot
 

Hi Guys,
I'm new here and this is my first post, so please forgive me if this subject has been covered before. If it has maybe someone could direct me to the thread.
I recently bought an '02 F250 super duty 4x4 with a 5.4l gas engine.

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