#5spark plug has antifreese on it and when your driving with the heater on the temp goes way up but if you turn the truck off then right back on the temp goes to normal ,the truck
does miss when cold then most of the time is fine when warm.

 

I am going to have to say that your head gasket is damaged, Check the oil and make sure there isn't antifreeze in it. Then you will definatley know it is blown