car stalls, then recovers, in motion

[heavyweight280]

1978 280z

I am trying to find what is causing this. The motor starts and runs almost flawlessly. Then at times, without warning, it will stall, usually while in motion, a couple times while idling. This is completely sporadic in that it may go days, weeks, even a month without repeating. No warning, just a quick jerk followed  compete loss of power for a brief moment that lasts half a second, 3-7 seconds, then another jerk and running fine again. Most recently it when it started raining heavy i had no spark for 40 mins. I know I have fuel, fuel pressure, so the problem is spark. I am thinking it is ignition related because I don't notice any disruption of power with radio, wipers or other electronics. While looking for clues I found this, mounted next to ignition coil. Looks beat up. What is this, will it cause these symptoms, and where can I get another?

[NewZed]

That's a capacitor, AKA condenser. It knocks down electrical noise from the ignition system.  If you have a decent meter you can test it.  You can replace it with an alternator capacitor or your Nissan dealer probably has one.  They're common to many cars.

 

Just because you have fuel pressure that doesn't mean that the injectors are opening and delivering fuel to the engine.  You can have spark and no injector opening, and get a no-start.  Best to confirm no spark, using a tester or a spare spark plug.  

 

Also, the EFI system has its own power supply.  You could have power to everything else, but none to the ECU and injectors. If your fuel system is in good order, it will hold pressure without the pump running.   Carry a good meter and a spare spark plug in the car, and have a testing plan ready for next time it happens.  There are a few key things that you can test within about 5 minutes, that will tell you more about what's really going on.

 

In the meantime you could open and clean your power supply and ground wire connectors to the EFI system.  Often overlooked since there's no reason to disconnect them.  They're exposed and they get dirty and corroded.