Slartibartfast

Like an OE Nissan one? That's cool, didn't know that was a thing. Makes sense it would be, though. Yeah, mine's not happy when it's really cold. Takes a few minutes before it'll go into gear without stalling out. Fortunately I've had nowhere to go so far during this cold snap. It was -19F yesterday morning! Can't complain, power's still on on and the plumbing still works.

I haven't done one on a VG, but I replaced one on a friend's Dodge last winter. Not much to it, provided the core plug hole isn't rusted to hell. They're not fun to do from under the truck, in the snow, so you've got the right idea doing it while it's on the stand. The heater I was replacing wasn't very old, so I'm not sure why it burned up. Didn't find any brand information on it. I don't remember what brand I replaced it with, either, but I didn't go with a cheap one, because I didn't want to do it again. IIRC the instructions on the site where I bought the heater said which core plug to replace and which way to point the element for that particular engine. It does a world of good on a carb'd 360.

Jeepers have rubber ducks, this guy has a real one! Dammit, now I want to see this, too. A guy on here turbo'd his VQ and was having transmission slip issues. Probably more hassle than it's worth in a rig that goes places where most tow trucks don't. 12 mpg is rough. Hopefully the gearing helps. I've heard of some rigs de-tuning themselves if they have smog codes--no idea if the R50 works that way, but that could explain a lot. The point of no return is always daunting. If it helps, you've got a group of Pathfinder nerds here cheering you on.

Oof. Tough to tell from the pictures, hopefully the damage isn't too deep.

Hell yeah! Looking forward to seeing this one come together. Nice that there's a kit to retain ABS. Is the tooth count on the GM tone wheels the same as the ones in the R50 hubs? I don't know if the ABS would notice/care about a mismatch vs the rear speed sensors, or if it's just looking for lockups. I've got a WD21 front driveshaft on the floor in my shop, let me know if you need measurements.

Nice when it's the simple fix! Good thinking using the fader to work out which output was which.

I see that your head unit and adapter connect using RCA plugs. I haven't set up a head unit like that, but the first thing I'd do is poke around in the owner's manual to see if there's some some setting you need to change to switch it over from the internal amplifier to the RCA outputs. I would also double-check that the RCAs are plugged into the correct holes--looks like you want the four closest to the power plug on the back. If it's not that easy, check fuse #4 (15A), in fuse box JB (looks like that's the one under the dash). That's the unswitched power feed for the audio system, and while the head unit may power up without it (it also gets power from the ignition switch), the audio amps (there are actually three of the little blighters) will not. If that fuse is blown, check your work, because fuses usually blow for a reason. Check your color code match-ups, look for damaged insulation/slipped-off heat shrink, make sure the pins aren't folded over in the adapter plugs, and make sure you didn't pinch a wire when you bolted the radio back in. If the fuse is good, and you test from the yellow wire in the head unit plug to ground, and you should see around 12v whether the key is on or off. The only other thing I see that could take out all the amps at once is the turn-on signal from the head unit, the one you mention in your second post. It should be blue/white coming out of the head unit. Confirm that this connects to the light green/red wire in the harness, and confirm that it tests at +12v when the head unit is trying to play music. If that checks out, I would try and track down the relay for the front speakers to confirm that it clicks when the radio turns on and off, or find the rear amp and verify that it's getting signal to the appropriate pin. The circuit diagram for the Bose audio system is on EL-145 of the '99 manual (download it from Nicoclub if you haven't yet).

Fresh springs sounds like a good place to start. I realized recently that what I thought were lift springs in my parts car are actually just the size they're supposed to be. The sagged-out springs in my '93 make them look like lift springs. Gotta get those swapped out one of these days. Those Sumosprings are interesting. Looks like a giant squishy bumpstop.

Huh. Now that I'm looking closer at the kits, yeah, those are just spacers! I had assumed that they were entire mounts. That makes it easy then! Especially if they offer a 50mm option. There's all kinds of good info in the service manual, but yeah, they don't make it easy sometimes.

Aftermarket body lifts replace the rubber body mounts with thicker ones. Nissan lifted the 4WD D21's cab by modifying the body mount brackets on the frame. This thread on Infamous has pictures showing the difference. The 4WD D21 brackets sweep up, while the WD21 and 2WD D21 brackets sweep down. The bushings themselves are the same (I confirmed one of them by part number). I have not confirmed that the D21 cab and WD21 body have the same spacing from the top of the bushing to the floor, but I don't see why they wouldn't, so I am assuming that they do, and that the difference in body height is entirely due to the brackets on the frame. Finding the height difference of those brackets took longer than I expected, but as usual, the service manual had the goods. All info below is from the BF section of the '95 service manual. I did not cross-check this information against other years because I've already spent far too much time in this rabbit hole and I would very much like to come out now. The BF section has coordinate measurements for a bunch of different points on the frame, including the body mounts. Each point has an X, Y, and Z value. I'm not sure what sets the zero point for the Z axis, but I know it's in the same place on either frame, because the front-suspension droop-stop bumper holes and the compression rod mounts match perfectly. (The front shock mounts do not, but neither do the part numbers for the shocks, so I guess that's just a D21 quirk that I was not aware of.) This means that we can directly compare the height of the body mounts between the two frames. I'll spare you the math--each one of the 4WD D21's cab mount points is exactly 50mm higher than the corresponding mount points in the WD21 and 2WD D21. In freedom units, that's 1.96". TL;DR: the D21 ARB bumper should fit a 2" body-lifted WD21. And yes, a body lift would leave a gap over the rear bumper, but you could fix that pretty easily. Slice the brackets, lift the bumper 2", weld the brackets back together. Even if you half-ass the welding, they'll still be stronger than the bumper they're bolted to.

The sealed-beam D21 grille and corner lights are no different in size than their WD21 counterparts. The D21's bumper matches up to its body the same as the WD21's bumper matches up to its body. The D21 bumper sits higher off the frame because the body does, too. So your options are raising the body to match the D21 bumper (which I know you don't want to do), or lowering the bumper to match the WD21 body. B posted some pictures of the mounts on his WD21 ARB, which should give you an idea of what you're up against. The top mounts look pretty easy to work with, but those lowers would need some thought. All things are possible with a welder, provided you don't mind cutting up a brand new $1100 bumper, and provided you're confident that your mods will be strong enough to take a winch. Take pictures if you do. I've read posts like this one saying that it should be possible, but I don't remember seeing anyone actually do it.

That Trail'd can is a cool idea. Their site says in a few places that their cans are for water, not fuel, though that may be an EPA thing rather than a materials thing. That said, I'd be a little nervous about suspending twelve gallons of gasoline over the road in a container it's not supposed to be in by a single chain hooked to a twenty-year-old hoist designed to raise and lower a spare tire. A secondary strap or even a skid plate to catch it if it falls would make me feel a lot better about it. And, yeah, accessing those in wet weather would not be a good time, though I don't imagine you get much of that in AZ. If you're planning to use the extra fuel often, I would consider mounting a permanent tank in that space instead. You might find a writeup somewhere like Expedition Portal, or wherever the Cannonball guys hang out. You might look at how Ford did it, too--they built a lot of dual-tank trucks, and I'm told some of them even worked right. Trouble is, the dual-tanks I've seen have a second filler neck, and I'm guessing you'd rather not attack your quarter panel with a hole saw. There's probably a way around this. Whether it's less work than fetching cans from under the truck, I don't know. Whichever method you go with, I would come up with a heat shield between the fuel tank and the muffler, and consider installing a trailer hitch (if you don't have one already) to protect the fuel tank from a rear-end collision. I doubt the unibody was designed to protect the spare tire the way it would've been to protect a fuel tank. I'll bet the tank off one of those oilless pancake compressors would fit in there real nice.

Is there a screen on a solenoid, maybe? I haven't had a solenoid out of one of these, but IIRC the solenoids in my friend's 4L60E had screens to keep junk out of them. I would write down the instructions for the blinky-lights OBD and keep that in the truck so it's handy the next time it acts up. Figuring out what it's actually upset about could save a lot of guesswork.

What sort of play? Rotating, radial? Either way, I wouldn't expect it to only act up on decel. How's the oil level/condition in the rear end?

The filter's not ringing any bells for me, but the AT section of the manual should show it somewhere if it's supposed to be serviceable.

Overfilled fluid could do it. The fluid level rises as the transmission warms up, so if the fluid's on the high side normally, a little extra heat could get it high enough to get air whipped into it and make the hydraulics act funny, which makes the computer think the sky is falling. Make sure you check it with the transmission warmed up, otherwise it'll read wrong. I overfilled mine by about a quart by believing the dipstick when it was cold.

I doubt the oil leaks are related. Any codes? If you can't get transmission codes through the OBDII, there is a workaround using the old blinky-lights OBD. The diagnostics for that start on AT-48 in the '03 manual. I don't know if they're like the WD21 where they only store the code for one drive cycle, hopefully not. The "judgement flicker" setup is a bit of a PITA, might be worth a try, though. Once you know what it's upset about, you can track down why. Any issues with the engine temp?

Worth a shot, I guess. Let us know if it feels different afterwards.

You're in for the same job as a body lift, minus the supporting mods to the fan shroud and fuel filler (though you may want to loosen those so you're not yanking anything when you jack up the body). I haven't done one, but from what I've read here, there's not much to it. Given how little you'll need to lift the body to slip the mounts out, you may not need to remove the front bumper brackets. The steering shaft may still put up a fight. It would be a good idea to have new bolts on hand, or at least have a plan for where to get them, in case the old ones do not come out politely or are otherwise not good enough to reuse. Are the existing mounts collapsed?

I do like that gen of patrols! You can keep the mud, though.

Frenchy, I believe you are confusing our early fuel injection with more sophisticated modern systems. Modern vehicles use wideband oxygen sensors, which allow their computers to dial in any air/fuel mixture they want, so they can stay in closed loop all the time (once the sensors are warm, anyway). These older rigs use narrowband oxygen sensors, which are useless* for any mixture but stoich (around 14.7:1). The narrowband can't even see stoich--it can only report rich or lean, so the computer bounces the mixture back and forth between them in a zigzag that averages out to stoich. This means these rigs can only run in closed loop for light acceleration and cruising. In any other conditions, they fall back to open loop, and run on stored values. A while back I added LEDs to my dash that mirror those on the back of the computer, and running the computer in one of the first two test modes lets me monitor the operation of the oxygen sensor while I'm driving. The green light flashes with the oxygen sensor when the system is in closed loop. I only ever see the green light flash under light-to-moderate throttle. Under heavy throttle or engine braking, the light does not flash. The light does not flash at idle, either, though I have seen it continue to flash briefly after the engine has returned to idle following closed-loop operation. I assume idle (even warm idle) is set a little on the rich side, and as such cannot be monitored with a narrowband sensor. (*There may be a little more going on here than I'm giving the system credit for. One of the test modes is supposed to tell you if the mixture is more than a certain percentage rich or lean in closed loop, and hell if I know how it's working that out from a sensor that only reads 0 or 1. Nissan may have done something clever to squeeze a little more data out of these primitive sensors, but clearly they were not able to get wideband performance out of a narrowband sensor.) Anyway, Teesetz, good to hear it's back on good behavior, and good luck tracking down any residual gremlins.

Wrong fuel pressure, unmetered air, and 30-year-old EFI that doesn't monitor the mixture at idle. Yeah, that makes sense.

I would never have called that being the problem! I'm guessing the incorrect fuel pressure was throwing off the idle mixture, which threw off the idle speed, and the computer ran out of adjustment trying to fix this and went to high idle. Still not sure why electrical loads calmed it down. In any case, good work finding it! Hopefully the issue stays gone.

If it's not isolated to the headlights, then tracing the headlight circuit might be less useful than I hoped. I would expect the alt to struggle more with the lights on than it does with them off, but I'd be curious to see battery voltage at idle, loaded and unloaded, when it's acting up vs when it's not. Was your defroster on when you heard it idle up on its own? The auto HVAC system kicks in the aircon when the defroster's running to dehumidify the air. Could be the compressor cycled and that's what made it idle up. It's been a while since I had working aircon in mine, so I don't remember how much it's supposed to idle up for that, but I don't think it was that high. I don't think the manual HVAC does that.

That's a weird one. I've had low idle/stalling issues with mine when the MAF connector was acting up, but I've never had it stick on high idle. And the headlights playing into it is bizarre. There is an adjustment on the IACV, and the procedure to adjust it is in the service manual. If you think it's acting up because the last guy messed with it, it might be worth ruling out. The crosstalk with the headlights tells me something else is wrong. Adjusting it to mask the current issue may complicate your diagnosis of what's actually wrong, or give you other issues. For some damn reason, these have two idle control valves. The IACV-AAC (the one under the back of the intake, with the adjustment screw) has a solenoid that's pulsed by the computer to fine-tune the idle. The IACV Air Regulator (the tall one behind the EGR, with the plug on top) is wired to the fuel pump relay and acts like the electric choke on a carburetor, except backwards (starts wide open for high idle on cold starts and slowly closes as it heats up). Test info for the two valves is on EF&EC 117 and 119 of the '95 manual. I suspect the valves themselves are alright, but a weak connection in the headlight circuit is confusing one of the sensors that tells the computer when it needs to raise the idle. The computer controls the IACV-AAC according to input from the sensor in the dizzy (which tells it the engine speed--you'd have other symptoms if this was bad), coolant temp sensor (idles up when it's cold--check the sensor and its connector), ignition switch (start signal, doubt that's got anything to do with it), throttle position (presumably so it's not thinking about idling when it's not idling--it is idling, so I doubt it's this, though it wouldn't hurt to check its adjustment), neutral position switch if it's an automatic, aircon switch (idles up when the aircon is on), power steering pressure switch (idles up when the power steering is working hard), battery voltage (I assume so it can idle up if the alty needs more RPM to hit its voltage target), and the vehicle speed sensor (I assume this is so it can work out if you're coasting or engine braking). If the valves themselves check out, I would go to the EL section, work out which fuse link and ground point the headlights use, and check them both. If any of those points are shared with other equipment, and are poorly connected, power could be backfeeding all over the place. Make sure the connections are clean and tight and the fuse links are in good shape. If that doesn't get you anywhere, I would check the sensors that tell the computer to raise the idle (EF&EC should have test info for each) and their connectors. Failing that, check the battery voltage at idle (with the headlights on and off), check the engine grounding (voltage from the engine to the negative post on the battery should be pretty low), check the other fuse links, and check whatever other ground points you can find. Look for any obvious harness damage. Wiggle stuff with it running, see if you can find something that changes the idle. Hell, check the vacuum lines, if you haven't, though I doubt they have anything to do with this. The '95 manual also has some basic troubleshooting, including various idle issues, starting on EF&EC-50. When it's at low idle (with the headlights on), does engaging the aircon or the steering switch (turn full against the stop and hold it) bump the idle back up? Does it idle down for just the parking lights, only low beams, only high beams, some combination thereof? And finally, does loading the electrical system with something else (rear defroster, blower motor, something like that) have the same effect?