You may have an intermittent ground connection. Passenger side of the block rear is a collection of grounds. Remove all clean meticulously and then the last on should be drivers side valve cover or cylinder head ground strap. Clean both ends no paint left under at the firewall. See what that does for the problem.
89 2.5 TBI, 4" RC lift, 1" Booms, SYE, Adams Driveshafts front and rear, Ford 8.8 with 4:88s, BFG 33X12.50X15, and a ton of other stuff.
AF Jeep Club Tail Number 184