Originally Posted by OVERtheEDGE
yeah same here its only a problem in the winter
My wife's old 97 Explorer had this problem, only when it was colder. It ran rough when it was cold out, until it warmed up. Turned out to be the upper intake manifold gaskets. When they were cold (and brittle) they didn't seal up right. Once they warmed up, they expanded a little bit and sealed up, ran fine.
I took a risk buy only buying the upper gaskets and replacing them fixed it. Sometimes it is the lower gaskets though as well.