If it is the 2.6l It could be the carb. I had a carb on my 1984 spx which had a 2.6l and the carb started cutting out randomly on hills. I wiould have to wait a little while, then it would restart and run fine for another misc amount of miles and then cut out again. It mainly did it on hills

8 Starion SHP, 87 mitsubishi van, , 81 galant g54bt, 78 lancer g54bt, 1965 Mitsubishi Debonair Deluxe
87 swb montero offroad pkg goin g54bt with sr locker 33x12.5 dual bouncy.