NewZed

The low RPM driveability problem is super common. Might be that /Nissan tuned the system to the edge for emissions on 1970's gas and it's too lean on today's gas. This fuel tweak really works.

Use more words! "Off" which way, loose or tight? "Rough" how? I mentioned the stumbling and bucking. Pretty typical to work your way up to good-running, through many small improvements. They're easy to get running but take some work to get to perfect.

They all go at the same time. Another thing to watch is the tachometer needle. If it moves smoothly with RPM that's good. If it jumps around for no reason or reads the wrong RPM, that's a sign of ignition module failure. The ECU's also go bad, usually running rich and rough, until they just die sompletely. Have you tried to drive it yet? These old AFM's are also known for running lean. If that's the issue the engine will pop back through the intake and buck and jerk when you give it light throttle, under load. http://www.atlanticz.ca/zclub/techtips/tempsensorpot/index.html

Burnt/bent/sticky valve maybe. Have you done cylinder pressure measurements? Should be at most 185 psi, depending on the gauge used. Maybe the PO shaved the head. Looks like you're doing everything right, for an engine with good working parts. There a couple of odd things though, I quoted above. 1978 used the N47 head. Why does yours have an N42 head? And what type of coil are you using, in detail. The ballast resistor is actually a device that changes resistance as ignition dwell changes. It's not just a resistor. It's not a well-understood device, but pretty ingenious. You might be overpowering the old 1976 ignition module. Zhoob's thought that you might just have spark crossfire seems to fit. Maybe you just have bad plug wires. Move them around while the engine is running and see if things change. Use an insulated screwdriver or wooden stick., or make sure your hands are dry. But here's some more possibilities. - The PO left the PCV port under the intake manifold open, either at the manifold, or at the side of the block. You missed a vacuum leak with your testing. - The PO connected your vacuum advance to "always on'; vacuum instead of ported vacuum. Check your timing at idle and disconnect the vacuum advance hose to see if it stays the same, It should. - The weights on your distributor mechanical advance have lost their springs and your timing is jumping around. Again, check your timing and see if it advances with RPM like it should. - the breaker plate in your distributor is gummed up and getting stuck at high advance. Timing light should tell you what's going on in there.

Sometimes that is caused by a flattened cam lobe. The exhaust valve doesn't open all the way. You might recheck your valve lash, examine the cam lobe quality, and also check your camshaft timing using the notch and groove. Cam lobes have been known to go flat very quickly. "After adjustment" is good. Make sure the drivers side of the chain is tight and the timing mark is on zero. Use the cam shaft bolt to turn the engine.

Wouldn't the ECU need a MAP sensor for vacuum advance of timing? Also, an RPM signal for centripetal advance. Does the 2J use a crank mounted sensor or does it use the distributor type CAS? Interesting idea. Might be easier to just modify a distributor that has vacuum and mechanical advance to work in the engine, to trigger an electronic ignition. Timing control is the hard part.

Your best option is to study the wiring diagram. That's why they were created. Read the FSM Engine Fuel chapter also, it explains the fundamentals of how an EFI system works. That will help you. The EFI harness is separate from the main harness for the most part. The gauges might take some work if the sensors are different between Nissan and Toyota. Getting the fuel pump control system to work will be difficult, probably. It's described in the FSM also. Using the Cressida EFI system in a Z or ZX is not common. You're kind of on your own.

What did you do to get it to fire? Are you saying that you had a bad ground?

CZCC.com has wiring diagrams and FSM's The FSM chapters typically have a smaller diagram specific to each area. I'd look through those. https://www.classiczcars.com/files/ Of course, you can also examine the wires at your shift linkage and the switches on your transmission. Here's a site I like to use to see which parts go where. Look under Powertrain and/or Electrical. http://www.carpartsmanual.com/datsun/Z-1969-1978

Tach input is the CAS signal. Tachometer is just a meter that measures engine speed, which is what the CAS does. You didn't confirm power to the coils yet. You have to have power to the coils. Power AT the coils is not provided by the Megasquirt system. Megasquirt provides and controls the grounding of the power. Look down at the bottom of this picture where I scribbled. https://www.msextra.com/doc/general/ms2external.html

Coil power typically comes through a fused switched circuit. The Megasquirt system grounds the circuit to control the spark but the power to the coils can come from anywhere. You might browse some of the wiring diagrams on the DIYAutotune site or see what you can find on Hybridz to see how people power their COP systems. I haven't used one so don't know if there is central point from which the coil leads split or if each one has its own circuit. Follow your COP wires back and see what's missing. I did a Google and found a few things. The first one uses the same words I did, so I might be on to something. There's probably a wire from your harness that you need to connect to switched power. http://www.megamanual.com/seq/coils.htm

Sorry, but you're going to have to dig in a little deeper. You didn't watch the video I linked, it shows how the three wire CAS works, You didn't answer the implied question about the Megasquirt software and whether or not it shows the CAS signal. Do you have Tunerstudio, or other tuning software? There's a bunch on the site about CAS signal problems. Since it worked at the supplier's shop the problem would seem to be with your equipment. The CAS signal is most likely. Here's one that covers a few things. https://www.diyautotune.com/support/downloads/ http://www.tunerstudio.com/index.php/tuner-studio/tunerstudioms-menu

I'd try to know more about these unknowns. You can waste a lot of time otherwise. You said that you have LS2 COP so there are no coil packs. There are two reasons a coil won't discharge - no power or no making and breaking the power circuit. You can probably check for power with a meter at a coil. The CAS can usually be tested also. Here's a typical video, it's actually pretty good. I don't see any reference to checks with a meter in your post. That's the place to start. Or, if I recall correctly, Megasquirt itself will confirm some of these things. Doesn't your "dashboard" show the CAS signal? Kind of looks like you just plugged things in and turned the key. https://www.youtube.com/watch?v=RvuzZJqQDf4

I hope I'm not leading you down a messy path. This module swap is fairly easy if you have electrical experience, but might be a bit tough if you don't. It is a very common ignition module swap it works on many different brands of car and motorcycle. If you want to do some more searching and reading, use "GM HEI module swap" on the Google. I assume that this is for your 79 280ZX? If so, it should work fine, using just one of the pickups, using just two of those three wires. You can just leave the other one disconnected (tape up the end to avoid shorting the other pickup). The "black box" is a GM HEI module, that you can buy from any auto parts store. Ask for a 1977 Camaro ignition module. It has two holes in it for mounting inside a GM distributor but you'll be using those holes to mount it close to your coil and distributor. The mounting screws need a good ground circuit, so don't mount it to plastic or rubber, find a good solid metal spot for it. https://www.rockauto.com/en/catalog/chevrolet,1977,camaro,5.0l+305cid+v8,1035111,ignition,ignition+control+module+(icm),7172

Don't know if you meant propeller shaft or halfshaft (drive shaft), but you can still get the "D" bolts for the propeller shaft, apparently. http://www.carpartsmanual.com/datsun/Z-1969-1978/power-train/propeller-shaft/2 https://www.nissanpartsdeal.com/parts/nissan-bolt~01111-00051.html

No. But that's where misalignment comes from, on all vehicles. Bad bushings and/or bent parts. Or loose/missing bolts. Check the subframe mounting bolts also. The whole thing could be about to fall out.

Get underneath and check the bushings, and look for bent stuff.

Here's a pretty good writeup. The most important part is the picture I think. There's almost too many words. Sometimes, if your distributor has been rebuilt you'll have blue wires instead of red and green. But they'll be red and green back inside the distributor where they spllced them in. Make sure that the mounting plate is well-grounded. That's where all of the current from the coil passes through. The C, B, W, and G that he shows will be molded in to the GM HEI module. The red and green wires from the distributor trigger the module through the G and W connection, and the B and C connections control the coil. There will be wires from the coil's negative terminal back in to the harness, those trigger the tach and the ECU. Just leave those as they are. http://www.sonic.net/~kyle/ztech.html

I thought that he said he got a magnet. Maybe he got the last one or they've stopped business due to the virus. https://www.amayama.com/en/part/nissan/22158s6700 A 280Z distributor will work just as well as your 280ZX distributor. The main difference is that the 280Z unit has an external ignition module. Might be easier to find a 280Z unit. @borini63 used to have spare parts.

Did you see this? You never said.

Pretty sure that the numbers are in one of jmortensen's threads. He had the shortened axles made. You could search his name or send him a message.

Maybe he just added to someone else's thread. Here's what I found searching jmortensen and laser.

I think that this guy found a source. Very surprised when he did. You'll have to read through it to find the post I think it's later in the thread. Start at the end and work backward if you're in a hurry. https://www.classiczcars.com/forums/topic/63629-hitachi-280zx-distributors/

Just make sure the centerlines of each are parallel. That's the key. Jmortensen has written up a description of how to do it, using a laser and some gadgetry.

Nice looking car. 1975 only has two fusible links, plus the one in the power line to the EFI system. So your car is normal. Do you know if the alternator is working? You didn't mention the ammeter or voltage measurements. Just that you replaced the battery because it died. The way that it started, drove, then died and won't restart could be the ignition module or the ECU, among other things. Do you have a meter? You really need one to make any progress on the EFI system, or just for working on a car, in general. See if you have power to the coil, power on each side of the fusible link, etc. You can waste a lot of time and money replacing parts, when a few measurements will usually identify a problem. Electrical parts that can crap out after 40+ years, if original - ECU Ignition module Pickup coil in distributor Fusible links Fuel pump EFI/fuel pump relay Several sites out there have service manuals that you can download for free. I'd get one.