After more than a little hair pulling, being stuck a few times, and replacing at least one part(20$ coolant sensor) unnecessarily, I found the problem on a 79 280zx. In the circuit between the battery post and the power supply for the efi relay, which supplies power for both the injectors and the ecu, there is a connection or lack of one that heats up and acts as a resistor whenever it wants to. This results in sporadic function of injectors/ecu. If you don't get power to injectors, look here.They'll show a hot, but the ecu grounding will tax the circuit beyond it's ability and you won't get ground. Only really consistent clue was it always started cold, and toward the end, usually wouldn't hot. FSM procedures won't find this.
Summary, if ya want a dependable car, first thing ya wanna do is check all connections and fusible links for any sign of corrosion or heat damage. They CAN be an intermittent pain in the posterior. I haven't done mine yet, I'm using a jumper to the battery until I get a chance to clean up the fusible link block, and it's running better than ever.(weather's crappy)

 

NICE! helpful, detective dude!!