Slartibartfast

Thanks for closing the loop! Nice when it's an easy fix.

Those do look like they might work. The only issue I see with them is that the diodes are facing straight in, and in both cases they need to be facing 90° out to light up the button face properly.

Could be a small injector leak flooding the intake with fuel vapor (which dissipates or leaks past the rings when it sits overnight). On your next warm start, try flooring it while you're cranking. That should put it in clear-flood mode (injectors off). If it's flooded, it should fire faster like that than it does normally (clears out the flooding faster when it isn't spraying more fuel on top of it). You could also do a fuel pressure leakdown test (hook up a fuel pressure gauge, prime the fuel system, see how long it takes to leak down). Also check your oil--does it smell like fuel?

I checked the hazard switch from my 6/'95 parts truck, and it has the same quarter-turn light socket as the aircon switch, right there on the top. If your '94 doesn't have that, it must've changed somewhere in between. The D21 was available in the US until 7/'97, so the socketed version should be easy enough to track down--or PM me, I have no use for the one I've got. That said, these are not that tough to open up, and if you do it right, you'll only have to do it once. Even if you get the socketed one, I would still solder the resistor and LED to the circuit board instead of trying to work around the socket. That could be done without opening up the switch. The bulbs in the sockets appear to be the same ones used in the rocker switches. And, yeah, they're not 74s; reading that link I posted properly this time says it's the HVAC head unit that takes 74s, not the switch.

It's a little fiddly, but honestly not that bad, apart from the pucker factor of working with 30-year-old plastic that needs to go back together when you're done or something on the truck won't work. And yeah, the marker light circuit lights up the front corner lights and the tail lights. I've got an aircon switch in my spares bin that I might have a poke at later if I remember to. I would be tempted to solder the resistor and LED directly to the contacts on the circuit board rather than try and re-use that little bulb holder. Nice that you can get to it without separating the housing, though. I forgot about the latching push-style hazard switches in the round dash. Looked one up on eBay and, yeah, looks like they've got the same screw-in bulb housing, so that's nice. Does the switch on your '94 not have that?

Looks like the rear ball joints are retained by a snap ring, so if you can find parts, it should be possible to swap them out. Unfortunately I'm only seeing separate bushings and joints listed for the front end on Rockauto, and whole arms only on nissanpartsdeal (the exploded diagram shows the arms with the joints/bushings installed). No idea if they match the fronts, or any other vehicle. You could compare bushing size vs your front end to see if they're in the right ballpark. Maybe pick up a set of used arms from a wrecking yard? If they're not better than what you've got, you could take them apart, get dimensions, and see if you can find joints and bushings that'll fit before you tear your truck apart. There aren't many active R51 owners on here, so you may find more info elsewhere. Good luck!

It's simpler than that. The dash illumination circuit supplies about 12v, which is what the incandescent bulbs were built for. The component LEDs I'm using in the switches want about 3v. Wiring a resistor in series with the LED limits current, which drops the voltage across the LED. Without the resistor, the LED would burn out as soon as it got power. I did not install resistors in parallel (like the Canbus bulbs do to simulate incandescent bulbs for fussier applications), and the switches do not illuminate when they shouldn't. There's no bulb monitoring going on in this circuit, and AFAIK there's nothing tricky that relies on them working like standard incandescents. The dash illumination circuit taps into the marker light circuit, so when the headlight switch is off, the dash illumination should be completely dead. AFAIK the only other components that could be supplying power are the alarm (taps into the parking light circuit so it can blink the lights when it does stuff) and the stereo (connects to dash illumination, I assume so it can dim the display at night). I would be surprised and concerned if either was leaking enough current to light up the switches, much less the switches, the cluster, and the marker lights, because, again, they all share a + feed--though at a low voltage, they may not all light up. (The dash lights ground through the dimmer switch.) That said, I have standard incandescents in my marker lights and my cluster illumination, so any stray current would have plenty of available paths to ground. If you swap every bulb on that circuit for LEDs, and end up with a ghost glow on the dash, I'll bet a couple of incandescent or Canbus-friendly LED bulbs in the front corner lights or the tail lights would sort it out. Looks like the aircon switch takes a #74 bulb.

I'm all about keeping stuff going, but between the structural rust, the rod knock, and all the other stuff you mentioned, it may be time to take that one out back.

Have someone work the wheel while you lay in front of the truck and have a listen. Maybe grab a few things and see if you can find the pop by feel. Might be something loose, might be a dry joint binding. I'm not familiar with the strut tops, but I'd check those, too. Hopefully it's something you can tighten or shoot some grease into, not something that'll need another alignment after you fix it.

You do have to take the switches apart to get to the bulbs. The bulbs themselves are tiny little buggers, about the size you'd find in a model train, with the leads wrapped around a rubber block that sticks onto some metal posts. I have converted all but two of mine (the two I can't reach without pulling the dash) to LED by removing the dead bulbs, and the rubber block, and soldering resistors and LEDs in their place. It's a bit tricky, and the switches are fragile, but it is possible. Separate the switch in the middle, where it's snapped together. This will take some screwing around to get all the snaps released at the same time. Don't try to remove the rocker on its own, you'll break the tabs it pivots on. Once it's apart, you'll see the incandescent bulb, which has a blue rubber condom over it. Work out the polarity (look at the plug--pink/blue is +, pink/black is -) and mark it so you don't solder stuff backwards. Work out how much of the metal tabs you'll need to cut to make room, so you can get the LED in the same place, with the bulb aimed at the rocker. This may take a little screwing around to get the LED where you want it and not interfering with anything else. I use 1k resistors and 3mm warm white LEDs. Test that the LED works before reassembling the switch, and make sure the rocker engages the sliding part properly when snapping it back together. IIRC there's a little ball and a spring that makes the rocker latch or pop back (depending on the switch), which may fall out when you separate the switch, so keep an eye out for those and make sure it all goes back together how you found it. One of these days I'm going to take my dash out again, and when I do, I'll convert those last two switches, and make a writeup or a short video on how it's done. Naturally this is not that day.

Check for any obvious damage to the OBDII plug, its pins, or its harness. Worst case you could check the wiring in the EL section of the service manual (free here) and check each wire. If there's damage somewhere, my bet would be the plug itself, unless someone's been playing around with the wiring. If that fails, the AT section of the manual has instructions for decoding the flashes without a scanner.

The W/D21 in the US all had EFI, so I've never worked with that particular carb. I would be tempted to tear it down and see why that venturi is loose, and what effect it might be having, but without a rebuild kit you might just get yourself into deeper trouble. The engine shouldn't be able to rev up much if the throttle blades are closed, unless air is getting around them, or getting in from somewhere else. Is there any high-idle setup on that thing? Wax motor that cracks the throttle when the engine is cold, or a solenoid to kick up the idle when aircon or power steering are active? I know some carbs crack the throttle open when the choke is set. Doesn't look like it is, but I would still have a poke at the linkage for that, make sure it's not hung up. Also make sure the screws for the throttle plates haven't come loose and let one of them shift enough that it's catching on the wall and not closing all the way. I remember some carb I worked on wouldn't close all the way until I loosened the throttle plate screws, let the throttle plate center itself in the bore, then tightened them up again. It could be getting air from a big vacuum leak (carb gasket, brake booster), but if the air's not going through the carb, the mixture will be way off, and I would not expect it to run well. Issues in the float bowl would make it starve or flood. Shouldn't make it run away.

Good work tracking it down! I like the Arduino scope, that's clever. I've heard of the gear on the sensor breaking, but the one in the transfer going is a new one on me. I haven't been into one, but it doesn't look like it would be terrible to get to, apart from the fun of working over your head on something that wants to leak fluids on you. Nissanpartsdeal lists what I think is the right part. The case is sealed with silicone, not gaskets, so at least you don't have to try and keep a gasket in place while you line stuff up. If both gears are worn, but not broken/chewed up, I would be tempted to replace just the one on the sensor, to see if that gave it enough engagement to work again. It's not like it's transmitting a whole lot of torque, right? Posting pictures here usually means hosting them elsewhere, unfortunately.

It's easy to forget about the diffs. They don't need attention very often, so they get put off and forgotten about. For the most part, they seem to hold up alright anyway, so long as the oil doesn't leak out, water doesn't leak in, and you don't beat the hell out of them. Like most things, the diff will probably last longer and run better if you keep good lube in it, but it's not gonna turn into the other kind of pumpkin if you don't adhere to the schedule exactly. Reminds me, I should change the oil in my front diff at some point. For all I know, it's been in there since the truck left Kyushu.

+1 for checking connectors and giving the computer a time out. I've got a loose MAF plug on my MPFI that makes it surge and stall when it acts up. I would also re-check the vacuum lines around where you were working. I have not worked with the TBI, but I've heard it can be pretty finicky, including running poorly with the air cleaner off. I don't have a PDF of the '87 manual, but I've got a PDF of the '89 up on Dropbox, and the TBI system is the same between those years AFAIK with the exception of some codes that got moved to different numbers, just to be difficult. (The '87 lists 42 as TPS, 43 as injector circuit, and 44 as no malfunction; all the other manuals I've got lists 43 as TPS, 51 as injector circuit, and 55 as no malfunction. The coolant temp sensor code did not change, so, no worries there.) The EF&EC section of that manual can tell you more about the TBI than I can. If you run into something in the '89 manual that doesn't match what you're seeing, message me, I've got a paper copy of the '87 and can cross-check if you want.

You won't know how bad it is (or isn't) until you get that tape off.

I would expect it to throw a check engine light sooner or later.

That's a weird thing to have missing. Nissanpartsdeal.com lists two different part numbers, depending on build date. If yours was built before April of 2001, you want 31086-4W000 (1/2000-4/2001). After, you want 31086-4W005. Both are listed as available. I have no idea what the difference is between them. Looks like you can punch in your VIN to make sure you're ordering the right one.

Sounds like you've tracked it down. I wouldn't expect a reed switch to fail intermittently, but maybe something came loose inside, or the contacts fouled. The contacts opening and closing might've worn through the fouling a few times before it stuck for good. Might also be the drive gear is missing a couple teeth, and sometimes it stopped in just the right place to where it wasn't driven. Hopefully you don't get it apart and then have to go track down a gear. The sensor pulling a 5v line to ground sounds reasonable to me. Could also be that the cluster or engine computer modifies the sensor signal in some way before sending it on to the transmission computer. I have no idea if those connections are straight through or not. Not sure on the fluid. Find the fill hole for the transfer and see if it's higher or lower than the speed sensor. If it's lower, then yes, you'll have some ATF come out to say hello.

Looks like the smaller of the red wires coming off the + terminal goes down to that wad of electrical tape, which I'm guessing is where it connects to whatever is left of the fuse links. I see a plug behind the battery there which is probably related. I also see a white wire cut off and just sticking up next to the steering res. Get the battery out of your way so you can unwrap that tape and see what kind of mess you're working with--and if it's not as bad as the wad of tape leads me to believe, find and check the fuse links, assuming they're still down there. When I replaced the + terminal on mine, I adapted the fuse link connection to the new terminal with a short copper bar. Bolts to the terminal on one end, bolts to the connector for the fuse links on the other. I assume the cable was used for the same purpose. Looking at mine again reminded me that most (?) of the links are short lengths of wire between two plugs, not loops from one plug. Worth noting, the wiring for the adjustable shocks is part of the starter harness and IIRC it goes right past the battery there, so don't go connecting wires just because they're there--make sure you know what they are first. Off the top of my head I think the adjustable shock wires are white with colored stripes, but it's been a while since I tore those out of mine. Again, the EL section is your friend. I'm also curious why one ground lead goes to the bolt it's supposed to be on, while the other one is on the clamp bolt, sitting all cockeyed. I don't think that's why it's acting up, but it ain't right.

It sounds like it's in limp mode. Exhaust getting that hot is probably due to the misfire (unburned air/fuel mix hits the catalyst and burns there instead). First thing to do is run trouble codes, see what the computer thinks is wrong. If that gives you a cylinder-specific misfire, figure out why that cylinder isn't hitting. If it's not cylinder-specific, could be mixture. Check the rubber tube between the MAF and the throttle body.

I read that as "change the oil more often if you're stressing the drivetrain." An empty roof rack should not be stressing the drivetrain.

The mechanic may not have thought to look for fuse links, or recognized our old-school fuse links when he saw them. If you don't find something obviously/visibly wrong, turn the key on, blower to full, and wiggle wires on the + terminal until you find one that makes the blower kick on. Might show you where the problem is if it's just a weak connection.

It's not the computer. The circuits that are acting up are not computer-controlled. It sounds like an issue with your fuse links, which are the small loops of wire plugged into the harness near the positive battery terminal. Fuse links are basically slow-blow fuses, and shouldn't pop on their own--hopefully if they are bad, it's due to corrosion or mechanical damage. If a link is fried or broken, or its plug is corroded, or the guy didn't reconnect the fuse links properly when he replaced stuff (sounds like he replaced the terminal?), that'll be why it's missing power to places. Could be the guy screwed up; could be something was corroded and didn't give you trouble until he flexed the harness to get the terminal off the battery. But, yeah, check that your fuse links are intact, and if the terminal was replaced, make sure the fuse links are still connected to it. You may also have an in-line blade fuse holder hanging off the + terminal if your truck has/had the factory fog lights. This is unrelated. The wiring diagrams in the EL section of the manual may help you narrow down which fuse link(s) aren't working right if you can't find the problem visually. Not sure about the trans hesitation. Is the fluid level correct? Might not even be the trans. Mine had an engine stumble just off idle for a while, and IIRC it was that damn MAF plug.

Sounds like a trans cooler line failed, and the fluid level got so low in the pan that it was sloshing away from the pickup when you went around corners. Hopefully it's just the rubber hose that's failed. I didn't know Matic D was still available! I used generic parts store dex/merc when I flushed mine. Annoyingly I think I paid about the same amount for it.