New World Datsuns...

Exactly. S13 is speed sensor. RB is mechanical speedometer gear, but it goes all the way up to the firewall on the Skyline and runs into a converter box for a speed signal.

Driven, the rostra one looks like a winner, but is the thread right? I have no idea if it's metric thread or not. But good find! And it's cheap $79 plus shipping, guess what that is? Oh yeah, just another $100 bucks, lol!!! I should put that on the license plate.

https://www.summitracing.com/parts/tgi- ... gJzxvD_BwE

Shit, check this out, for Toyota. Not the pass through like I wanted, but I do wonder if the Datsun is 22mm thread. Which actually, is really close to 7/8. Hmmm. I'll have to get a GM cable and see if it screws into a spare speedometer gear I have laying around.

I'd be really surprised if that doesn't screw in.

Well I ordered the Rostra GM one. Haven't confirmed thread yet. Fuck it, I'll make that bitch work one way or another.

CONFIRMED:

Datsun speedo gear attachment end is 22 x 1.5 mm, whereas the GM speedo gear attachment end is 7/8-18. So that means we have a speedo cable that is .86614, and the GM version is .875, which is .00886 difference. Almost 9 thousandths. Which isn't too much. But it's probably enough that the cable won't thread on. Thread pitch is probably close enough. What I'm thinking is I'll get a 22x1.5 die and recut the plastic threads on the Rostra unit, should be golden. Depending on how much slop there is, I may be able to thread it on and cut the new threads with the existing speedo cable end.

Either way, it should be able to work without much issue. Pretty sure the square drive is the same size between the two, but I'll just wait until it comes to confirm.

Okay, got the dash back together. Found my reason for the odo not working when I took apart the original instrument cluster. The little shaft broke the plastic tab out of the thing it was holding onto, and spit the gears. I ended up cutting the plate and filling it in with sharpie so you couldn't see it. The trim rings covers the rest of it. Then it's just one screw and you can weasel the odometer out of the speedometer housing without taking apart the gauge.

The only thing I don't have now is the high beam indicator and brake light indicator. Those were rectangles in the middle lower of the original speedometer gauge. Couldn't figure out how to nicely cut them out on the next Maxima backing, so oh well. I was going to wire them into the other warning console, but both the brake and high beam lights are in out contacts, whereas all the warning lights in the upper middle extra panel are common ground with a positive to each one. Short of it was, I'd need to interrupt the circuit board and then jumper it and it was going to be a big pain in the ass. I'm pretty sure I can figure if the brake's on, and high beams I hardly use, much less people will flash you if they're on. Either way, it's back together.

Waiting for the speed sensor to get that wired in. Yanked off the IACV, letting it soak in MMO right now, actuated it, seems to be doing better. Haven't yanked the bimetallic spring air bleed rotary disc, but have a spare I've tested that works well. Theoretically I should be able to fix the idle issue no problem. Unless of course it's a signal problem, and I haven't checked that yet. Figured I needed to clean these it anyway. Enjoy the pics!

That looks mighty fine

Thanks, I'm not 100% happy with it, but it's close enough to work and really, no one except me will probably look at it and know it doesn't fit perfectly.

Back onto the IAC valve. So I took it off and cleaned it. It wasn't terribly dirty. Verified the solenoid does work without issue. So if I start it up right now, it idles at 2000-2100. If I disconnect the IAC valve connector, it idles at 1100. I adjusted the air bleed, makes it idle higher, but not lower, or at least only gets me back to the 2000 rpm annoyance.

This leads me to two conclusions:

1. ECU is sending the IAC the wrong signal.
2. Bi-metallic spring disc plate valve is stuck open.

And I suppose 3 could be bad IAC. However, it changes with air, and with disconnection of the connector, so I'm pretty sure it's working. I also have a weird whistle resonant noise that almost sounds like a belt squeak, but it's not. Sprayed windex on the belts, no change. Didn't have a water bottle handy. Anyway, the little disc air bleed bi-metallic spring thing I think could cause that noise, and if it's stuck open, it probably won't matter what the IAC does, it will screw with it. Or at least, I think so.

Anyone else have any ideas on that? I still can't find any vacuum leaks, I thinking it's internal. Engine responds well when revved.

https://www.sau.com.au/forums/topic/272 ... 0rpm-idle/

Hmm, lots say IAC, all internal parts looked fine to me. I could watch the plunger operate while alligator clipping it to the battery. Some mention that TPS. I DID fiddle with it, but only after this problem started. Perhaps it's still annoyed. I should do more checks on it.

EDIT: Ah hah! I read further, they call the IAC the bi-metallic spring do-hickey. That's the one under the throttle body on the intake. The AAC (the one I cleaned) is the solenoid version on the back of the intake manifold. I'll yank that other one out tomorrow and examine it. I'll bet it's stuck wide open.

Now that I think about it, it makes total sense. I'll confirm it later this morning, but I already ordered a new one from Tacoma Nissan. Fortunately they had one in stock. Should get it Tuesday I hope. Being Japan is still screwed with coronavirus, figured I'd better order it while I can. RawBrokerage had to cancel a bunch of my gaskets because there was no eta due to the pandemic. Fortunately, this should be the last (he says while laughing) of the things I need to start driving her to work reliably. This and the speed sensor I still have to retrofit.

Idle air control/regulator valve part number is 22660-01U10, fyi. And this one is a different bimetallic spring thing. It has a 4 bolt square plate, unlike the older Maxima/Z round disc that has the same function. If the connector end worked, I think it would probably work the same, but I don't want to make an adapter and try. Just rather have the right part.

Booyah! Now to install and have a happy idle! EDIT: IT'S THE TPS, NOT THE AIR REGULATOR!!

So yeah. You know that old adage about free information on the internet? Turns out the throttle position sensor can make it idle at 2000 rpm. It was also mentioned in that thread. So at least I now have a new vacuum regulator. I put it on, and no change. And finally I tweaked the TPS ever so slightly and wouldn't you know, it came back down. 850 rpm. Perfect. So that was annoying. But at least it's one less old thing to fail I guess. I think the TPS was good, and probably just was right on the edge of perfect and then some heat soak and boom, screwed with the values. It was perfect and I didn't change anything until after the idle thing happened.

Anyway, so got it running nicely again and figured I should do a full 7k rev to make sure it went all the way. And there was a pop. And the engine shut off. After a few minutes of searching and shitting my pants, I found the intercooler hose at the intercooler in the fenderwell was missing a clamp. And it chose that moment to kick the hose off the intercooler. So lucky me, I didn't kill it. Scared the shit out of me because I saw the pop with a burst of dirty air and I thought I might have killed the turbo or something. Somehow I just missed a clamp.

Anyway, at least she's running well again. Haven't gotten the rostra speed sensor yet, that's the last hurdle minus a couple things.

Inspiration! Though it's a small nose Bluebird and an FJ20 engine!

Alright, the Rostra speed sensor came. It's metal, not plastic. That makes things a little more annoying. Also, the threads are already dinked up on one end so the adapter they sent doesn't want to thread on. I don't know if this is going to work like I planned, but I'll figure something out.

So it looks like it will just thread right on. Only problem is the Rostra GM one comes with an adapter end that is just a piece of square speedo cable. The Datsun one of course, has an end on it that has a fin for the speedo gear. So if I want to use it, I'm going to have to cut off the end and then either weld, or silver solder it or something to keep it together, after I press it into a square. Yeah. Not the easiest. If the clip into the speedometer wasn't a clip, I'd just get a GM cable and put that on.

At the moment, I'm not sure how I'm going to make a speed signal work. I'm thinking I need to make a little tiny tone ring off the diff or something. I actually also though about a propeller adapter and just putting it in the air stream, lol. Would work just fine.

Pitot tube? LOL