va slim

im new to the forum scene, so bare with me, i have a 86 4runner w/ 22re in which #4 fuel injector will not fire, i moved # 2 connector to it, and it fired, leaving me to believe the problem lies in harness. i found the splices and they were good, shorted blue wires on connector back to transistor plug on firewall to prove continuity. tested ground also the same way. still doesnt fire. getting frustrated please help