Zed Head

I'd check the coolant temperature sensor resistance. Compare to the chart from previous. Check at the ECU connector.

Could be the front seal or the front cover gasket. Both require removal to fix. Use a piece of wire or a long skinny stick in the fill hole to see how low the level is.

Do it again!

Browse through the Knowledge Base area. The articles are oddly categorised, but there's not too many. I found one in Body and Paint, pretty sure there is at least one more. Edit - actually, it's in the same place. Copied link below. https://www.classiczcars.com/articles/

Your number is in-spec for a 77 external regulator.

I'll go ahead and ask before CO does - is your ported port 70 mm across? Doesn't look it. 70 mm would be outside the 60 mm centerline of the screw holes. You'll need an adapter with a neck-down transition. Kind of defeating the point. They make a 60 mm big bore. Looks like it would fit about perfect. One example. There's probably used on eBay. https://zcardepot.com/products/big-throat-borla-throttle-body-60mm-280z-280zx

Is this for a factory stock head and intake manifold? Most of the horsepower chasers say that the intake runners and head ports are the significant flow restrictors. One of the reasons I remember that the ZX TB bore is smaller is because it was kind of surprising that they modified the L28 extensively for emissions and power and ended up with a smaller TB bore than the N42 based Z engine. Call me a buzzkiller...

I could be wrong about the Z versus ZX fit. But I have clear memories of different patterns. Anyway, here's some old instructions that imply the same TB fits both. Maybe the holes are slotted. http://xenonzcar.com/s30/files/Weber 60mm TB.pdf

Oh. Be careful with any information you find or get. I see some bad guesses out there. ZCD is selling a throttle body that he says will fit both Z and ZX. But I know that the bolt patterns are different, I've had both. My memory says that the ZX pattern and opening is smaller. A ZX TB will not fit a Z intake manifold and vice-versa. Surprised that he doesn't know this. https://zcardepot.com/products/big-throat-borla-throttle-body-60mm-280z-280zx?_pos=8&_sid=7968a8baa&_ss=r https://zcardepot.com/products/throttle-body-gasket-70mm-large-280z-280zx

You could go to an auto parts store and measure or buy a gasket. Don't you have a manifold to measure from? https://www.oreillyauto.com/search/v/a/6635/automotive-car-1976-nissan-280z?q=throttle+body+gasket

Another thought - a dead spot on the AFM wiper. You might be able to test that by manipulating the throttle by hand until you hit the zone, then moving the vane to see if it goes away.

Watched the video. The problem seems ready made for a timing light for a plug wire and a noid light for an injector. I don't think that "hunt" is the right word for the problem. Sounds like you're losing either ignition (which will also kill injection), or just injection. You're losing all six cylinders at the same time, not even a sputter. Seems electrical for sure. A noid light in parallel with an injector and a timing light on any plug wire, pointing at your face while you sit in the driver's seat, while you do that test should tell you something.

You can wire up the HEI module directly from the distributor wires and the coil power supply right next to the coil. Forget about the ballast resistor entirely, at least for a quick test. Or just use it as a terminal block. The HEI module is current limiting. The stock module is about 4.5 amps, I think, and the high performance ones about 7. But that's just at the beginning of the coil charging cycle. Should be fine. It's all about heat and you can touch the parts to see how they're doing.

Doesn't look like you tried. You said you were on the edge and passed on the next run-through. Therefore.... Keep an open mind. The 280Z EFI system is an excellent learning tool. Good luck.

The "proper" way to adjust the fuel-air mixture at idle is with the screw on the side of the AFM, not the spring inside. It's described in the FSM. Edit - actually, it's described that the bypass screw is not to be adjusted. But it is the most direct way to lean out or richen the idle mixture.

A carb'ed engine would have a low volume low pressure pump. No reason for it to be loud.

Have you had a timing light on it? Not clear why it would hunt at 2000 RPM but not at idle. 2000 is in the range of the centrifugal advance slope. Have you been inside the distributor? Engine RPM = twice distributor RPM.

I haven't experienced it, only read about it. Most people see it with a timing light. The mark is erratic. You could switch them and see what happens. The voltage and current is the same.

Are you sure that you need that for your vehicle? I only had to do the idle test. I lived in unincorporated Washington County though. plus, they will test your car for free, multiple times, as long as you're making progress on meeting the standard.

Actually, I might have my ammeter signs backward. Could be S is going open, as SteveJ suggested. Anyway, my point was about the possibility of funky wiring.

Rolling back to the original alternator wiring thread - seems like the L wire going open circuit might cause the ammeter issue. Might be two separate issues here, a dying starter and problematic wiring. How about some current pictures of the alternator and its wiring today? Especially the L circuit wire. Might be illuminating.

If I understood your first alternator wiring thread you have swapped in an internally regulated alternator. Linked below. But, there's no guarantee that it has not failed. Might be worthwhile to take it in to a parts store and have it tested. https://zcardepot.com/collections/charging-starting/products/alternator-high-amp-80-240z-260z-280z?variant=19280584015985 This alternator is rated at 70 amps and bolts up in the same location as the original. Internally regulated.

I saw that too. I wondered if the starter motor was getting stuck on.

There was a whole long thread a couple of years ago about this car. A swap to an internally regulated alternator, with a jumpered plug. I got confused just re-reading my own comments in the thread. Not sure I was helping. It ended with "new battery". Not so sure now...

How about this? Should be in your memory. The other wires look normal.