4.6runner:
Welcome to StangNet!
I am not much of an electrical wizard but the problem could be the wire harness that goes from the body (fender) to the door, the actuator, or the wire in the door to the actuator. If you move the wires around in the rubber accordian boot and the actuator works more reliably, then you know that the problem is in that part of the harness. Next, you have to check the actuator. If it hasn't been lubed for a long time, it might be sticky. More likely, it is starting to fail (hot weather makes things worse, right?). You'll have to pull of the trim panel (carefully) to get access to the actuator. You can use a small mirror and a strong light to look at the actuator and the connector. Pull of the connector and check voltage at the actuator. Lubricate all of the pivot points in the locking system. If that helps, that's probably all you need to do. If none of these things do the trick, it is most likely the actuator. The actuator is held in place with a rivet that you'll have to drill out (carefully) if you need a new actuator. You need to hold the new one in place with a rivet, too, so have a quality rivet gun handy.
HTH,
Chris