Mitsubishi Repair: mitsubishi expo, free hope, autozone

Question
my expo was running great till yesterday I was in the hwy and all of a sudden it started running really rough when you go into 4th and then 5th.  If you are going down a hill it picks up speed and the roughness isn't as rough. Does it sound like I need a tune up maybe a spark plug not firing?

Answer
Patty: Hello. No year was given on the expo, so I would try the tune up and if that does not fixed your problem. Then I would take the car to an AutoZone and have the car coded. That would check for any sensor(s) what might be weak/bad and how your computer is doing. AutoZone will code your car for free. Hope this helps and good luck!