Captain Obvious

These Z-Cars don't go off unless you hit them juuuuusst right.

You don't backfeed through the transistor. You backfeed through the other injector(s). Maybe these sketches will help with the weirdness. Here's why you would see +12 on both sides of the injector connector if you pull just one: And here's why you should be able to determine which side is which if you pull all of them (or at least the ones that share a transistor):

Good eye!!

I just did the internally regulated alternator modification and as a side benefit of doing that work, I now know the charging systems inside and out. Armed with that dubious knowledge, I discovered a mistake on the 77 color wiring diagram. Inside the voltage reglulator, some of the components are misplaced: Not sure it's enough to warrant revision "L" or save it until there's more, but if I didn't write it down, I was going to forget! This wiring diagram is better than sliced bread. Way better!

Well the symptoms say "lean miss", but the SM needles say "richer than necessary" at almost all points. Only place they are leaner is way way up by the shank. I would expect that you're above that area at pretty much any spot except maybe idle? In your original post, you said that you "seated the needles against the seats". What do you mean by that?

There's no pull ups on the injector outputs inside the ECU. However, unless you pull all the injector connectors off at the same time (at least all the ones that share the same transistor) you'll read 12 back feeding through the other injectors and their dropping resistors. In other words, for example... If you pull the connector off injector #2 and probe the contacts for voltage WRT ground: One side will read 12V because it's pulled up to Vbatt through it's dropping resistor. The other side will ALSO read 12 volts because it's pulled up through the solenoid coils of injectors #1 and #3 through THIER dropping resistors to Vbatt. If you pull all the injector connectors at the same time, you should be able to determine which side is hot and which side is pulled to ground by the ECU. Does that make sense? Did I say that right? :bulb:

In addition to pulling off the cover over the ECU, I think you'll want to remove the small trim strip that runs horizontal above the driver's knees. I don't think there's enough room to swing the big ECU connector off it's bottom hook if you don't take out that trim panel as well. Before you start poking around at the ECU connector... Have you checked the big fusible link(s) that feeds the whole fuel injection system? Goes right from the battery to the FI harness? Spade connectors on both ends to facilitate replacement if necessary. You should have 12V on both sides of that link at all times.

The SM needles should run richer than stock and there's no reason you should be running lean with them. They should be capable of delivering more than enough fuel for your motor. Can you get your hands on a wideband to help nail down if it's a fuel problem or not?

The garage is calling. The mice want company too. :laugh:

You got sparks at the plugs?

I'm bidding them to please take that memory away from me and let me forget I ever saw that ad. Unfortunately, I'll never get those thirty seconds of my life back. :sick:

Unfortunately it's down there somewhere:

I would agree with your assessment. The oil is there only for transients. If you're keeping a steady foot, the oil doesn't do much of anything. Might apply some "anti-oscillation" damping for the loop, but other than that, it's a non-factor. Also, if you can punch it and it doesn't sputter or bog, then that's another data point indicating that your oil is of a suitable weight. As for the problem you're having... Are you sure it's not an ignition issue? Timing slipping around from sloppy gears or bushings or something? How do the plugs look? Can you tell if you've got a mixture issue one way or the other?

I'm no cooling system expert, but I think it's important to have a small amount of flow through the thermostat housing, even when the engine is cold. If that area is completely stagnant, then you run the risk of overheating because the thermostat won't be subjected to the hot water and could instead be sitting in a stagnant cold pool. I believe most thermostats have a small bypass hole built into them to allow for just this kind of issue, but I wouldn't completely block off all those path(s) without first confirming that is the case. Eventually heat will make it's way into that area through conduction and eddy currents, but if you don't ensure some flow somewhere prior to the thermostat getting hot enough to open, it may be too late by the time it does.

Yup, that's the thermostat that's supposed to be on the coolant lines through the manifolds. I'm assuming that most of them have failed or corroded thru over the years and have been discarded and replaced with simple nipples instead. That would be my explanation as for why you don't have one on your car right now. Can't tell from the pic, but is the nipple on the rear carb made out of brass? If so, it's clearly a later mod.

Yes, you are reading those pics correctly. The tensioner piston is no longer in the hole in which it is supposed to live. It somehow became dislodged and is probably swimming with the fishes down in the oil pan. And yes, in addition, since this is an unaccounted for unmetered source of oil flow, it could certainly account for slightly lower oil pressure. Sorry you're going back in again. Just when things started sounding like you had reached the bottom of the curve? You don't get a break, do ya?

Referencing page ET-4 in the 73 FSM... In 73 and 74, there were actually three parallel paths for water to flow through the carb and intake system. All three of them originated from the lower portion of the thermostat housing (the upstream side of the thermostat). From there, they split to three different routes: A) Through the balance tube. Through the intake manifolds. C) Through the carbs themselves. All three of those different routes then rejoined in the plumbing back by the firewall before wrapping around the rear of the engine above the bell housing and then heading back to the inlet side of the water pump. The blue hose appears to be the one that goes through the intake manifolds. Of those three routes, only the route trough the carbs themselves is thermostatically controlled, and that route has been removed completely when you swapped to the round tops. The other two routes are (supposed to be) as free flowing as the small diameter lines will allow. And from what I've seen, they are often so plugged with crud that they might not be passing any fluid at all. I think it's important to have a small amount of flow through the thermostat housing, even when the engine is cold. If that area is completely stagnant, then you run the risk of overheating because the thermostat won't be subjected to the hot water and will instead be sitting in a stagnant cold pool. So a far fetched theory might go like this: If the coolant paths through the balance tube and intake manifolds are plugged with crud... And the path through your flat top carbs was not... And your thermostat does not have a small bypass hole through it... Then you might have caused yourself a problem when you swapped carbs by causing a stagnation in the area below your thermostat that did not exist with your flat tops.

OK, I'm going to try one more time and then I'm really sorry, but I'm going to have to give up. Look at this pic. This is the part you are looking for: See the part with all the arrows pointing to it? That's the FICD that boosts the idle when the A/C is on. That's the part you are trying to find. You suggested that it is part of the EGR system, but you are mistaken. It is not part of the EGR system, it is the FICD and it is part of the air conditioning system. You don't have one on your engine because you don't have air conditioning. I don't know where to get one except used off a car that has A/C.

Despite the independent looking circuits, all six injectors are fired at the same time. Always. However, there are two output transistors in the ECU and they divide the task in two. One of the transistors does 1, 2, and 3 and the other transistor does 4, 5, and 6. The DROPPING resistors do it 4-2, but the ECU does 3-3. But, since the control signals to both transistors are tied together all the injectors are told to open at the same time.

Yeah, I've heard the same as well about one side being NLA. I'm thinking that the guy who owned the left hand thread company had dirt on the suspension design guy at Nissan.

He's been on Craigslist off and on for a little while now as well. 240Z,260Z,280Z projects and parts Datsun "who knew "ugly" was camouflage?" Hahahaha!!!

Both of the inner tie rods have right hand threads and can be assembled onto either end of the rack. And yes, the outer tie rod ends are the same except for the RH vs LH threads. You could use all the same parts on both ends and just make up for it when doing an alignment. Not sure why they went through all the trouble to have the two sides different in the first place. Seems like a lot of extra expense for no "real" benefit.

I used a device called a "blind bearing puller" which is an expanding mandrel on the end of a slide hammer. You put the mandrel though the inner race of the bearing while it's down in the housing, expand it until it's tight, and then use the slide hammer to "knock" it up and out of the housing. Prices for such a tool are all over the map depending on quality. Here's a pic of one such device. This one is a little over $50 on Amazon:

I agree. That resonates with me as well.

You're still mixing thing up... Part number 4 on the drawing has nothing to do with A/C and the part that DOES raise the idle speed for A/C is not in that pic at all Here, maybe this will help?