It's the guts in your distibutor.
Most vehicles of this vintage used a magnetic pickup to trigger the spark. Ours uses a turning disc with 2 sets of information slots. A couple LEDs shine thru the slots and tell the ECU what the engine doing. It sinces top dead center and cam position. There are a code for each.
The 89 was a unique year to it's module. The system being a hair more primative on emmissions, etc. than 90-94 3.0s. Mine still has the original module at 245 K. The diodes can get weak or burn out. I carry an extra distributor with me when on long trips and when I go way back in. A new distib. runs like $250. I can't see buying a whole distibutor when I can't even picture how one in a 3.0 would wear out. The shaft is real short,not much torquing against the bushing.