94 Ranger Runs rough after 100 miles
 

My '94 Ranger XLT 4.0 Automatic runs fine until I take it on a long trip. If I drive it 100-150 miles at freeway speeds (65-75 MPH), it begins to act as though it's running rich. If I park it and let it cool for about an hour, it's fine until the next 100-150 miles. Could this be the computer heating up?

94 Ranger Runs rough after 100 miles