Slartibartfast

The service manual has a table with front/rear brake pressures with the truck loaded and unloaded. The adjustment procedure has you hook up pressure gauges on the front and rear brake circuits and check the bias loaded/unloaded. Adjustment looks like a really vague process, with the allowable range for loaded/unloaded overlapping each other. The WD21 and the 2WD R50 don't even have LSVs, they just have a fixed prop valve in the master cylinder. I'd expect an LSV without its linkage to act the same as the fixed prop. Provided the rears don't lock up first, it's probably fine. Might be interesting to do some hard braking tests to see if you can tell the difference between the LSV at its maximum and minimum settings.

I've bought quite a few parts from Rockauto, but it takes a little screwing around to make the shipping make sense. Amazon's got free shipping, RA's got cheaper parts prices, so which one I buy from usually depends on how much I'm buying at once and whether RA's got it in the same warehouse (they combine shipping if the parts are shipped from the same location). There's also a Rockauto discount code thread on here somewhere. If you want OEM stuff, there are a few dealers online you can check (including Courtesy Parts and factorynissanparts). OEM Surplus has some odds and ends you might not find elsewhere, though I haven't bought anything there myself.

Dim light/fluctuating with bumps sounds like a wire or sender issue to me too.

You can download the factory service manual here. The diagrams you're looking for are probably in either AT or EL. The AT section has some diagnostics that might help too (once you scroll past the instructions for using Nissan's CONSULT system). I would've expected a TPS fault as well, too bad it wasn't that simple. Good luck!

ATF in a cylinder will make it smoke, yes, but that doesn't really tell you anything. The usual test is to check compression dry, then shoot a little oil down the bore, then check compression again, and if your compression gets way better, that suggests your rings are junk (the oil is helping them seal). If the compression's still trash, that points to your valves. A leak-down test pressurizes the cylinder with air (with the valves shut) and seeing where the air escapes. Using a smoke machine instead of just compressed air means you can see where the smoke's escaping instead of just listening for the leak. What to do depends on how excited you are by the prospect of tearing down a VQ and how soon you need it back on the road. If it's urgent and you'd rather not screw around, chuck an engine at it. If you're intrigued and have some time on your hands, open it up. Either you'll find the problem and fix it for less than the replacement would've cost or you'll find that it's properly buggered and have an excuse to chuck an engine at it. There's some good info here regarding which engines will swap into yours. Good luck!

Is it losing coolant too? It is possible to get milky schmoo under the oil cap just from short trips and that don't get it warmed up properly. I'd want to do some investigating before blaming the head gaskets, just to be sure I wasn't chasing my tail taking it all to bits. The factory service manual is a good place to start. You can download yours here. I'm honestly not sure what the difference is between the '01 and the '01.5--hopefully someone with an R50 can chime in on that. Either way, the EM section will be your friend on this job. (I recommend downloading the whole manual while you're there so it's handy when you need something else later.) The manual shows where sealant is needed, how things go together, and what the torque specs are, and should help you build a list of the other stuff you'll need. This walkthrough is for applying threadlocker to the power valve screws to prevent them from falling in as they sometimes do, and includes gasket part #s and tips for at least the upper part of what you'll need to mess with. (It's also a good thing to do while you're in there.) Hopefully your oil loss is just a leak. The VQ in my dad's '03 didn't leak externally (that we could find) but it burned oil like crazy.

You've got it. The clutch pack can only hold so much before it slips. The breakaway numbers in Hawairish's table above are how much torque the diff is supposed to hold when bench-tested (one axle held, torque wrench on the other). That number may improve a little under load as the spider gears push out against the clutches, but if you've got a wheel off the ground, you probably won't have enough load to make a difference. Apparently you can use the parking brake to add load and make the clutches grab a little better if you're struggling. I knew the later models were de-tuned, but I didn't realize it was that bad! '03-'04 got screwed! I'm guessing the limited slip didn't play nice with stability control. I've heard of the LSD making chattering noises if it was refilled with the wrong fluid. It's supposed to run oil with a friction modifier to keep the clutches happy (that's why it says LSD oil only on the sticker). Without that, the clutches bind up, make noise, and have a bad time in general. The only noise I've noted from my rear end was a faint hiss that I thought might be the sound of the clutches slipping, but I'm not certain it wasn't just the wheels slipping in the snow that I was stuck in at the time. If you're looking for an easy swap to a better LSD, the early Xterra rear third member is supposed to bolt right in. CJ Franger on the NPORA facebook page (probably on here as well, not sure what his screen name is) put one in his R50 a while ago. Because it's a 3rd member style rear end, it's completely bolt-on without having to mess with gear lash or clutches, and it looks like it gives you more than double the breakaway torque of what you've got.

Also worth noting that the bearings don't necessarily need to be replaced. Mine were a little loose when I got the truck, but still looked fine, so I just repacked them and they were fine. (I did have to adjust tension again a while after, apparently they can settle in with time.) Mine weren't loose enough to make noise, though.

+1 to what the others have said. Sounds like the rear wheel on the other side was spinning. When you're in 4x, the front and rear driveshafts spin at the same rate. There's no differential in the transfer case to bias torque front or rear, so the front and rear diffs turn at the exact same rate. Each diff applies the same torque to both wheels on its axle--but if one wheel doesn't have enough traction, it spins and the other doesn't (the torque it takes to spin the wheel without traction is not enough to spin the wheel that does have traction and is trying to move the truck). If the truck is on uneven ground, it'll have less force on two wheels diagonal from each other (think of a four-legged bar stool on an uneven floor). If the suspension can't keep the wheels in good contact with the ground, those two unloaded wheels spin while the truck goes nowhere. Look where your tires are in your wheel wells, your driver's front is drooped way down (unloaded) and your driver's rear is stuffed into the wheel well. The passenger's front and driver's rear were supporting most of the truck's weight, so the other two had bugger-all traction and the truck wouldn't climb. If you don't have one already, you might try and track down a limited slip rear end (identified by an orange sticker next to the fill port that says LSD OIL ONLY). I like the limited slip in my '93, though it does have its limitations. IIRC the R50 LSD was toned down a little (probably because LSD makes it easier to make the rear end step out if you drive like a maniac. The LSD can be repacked to tighten it up. It's not as good as a locker but it's much better than an open diff IMO.

Hopefully that's all it was! I can't say I've noticed any warmth in my ignition wiring, but then I can't say I've felt the wires while I'm driving, either. I'd be inclined to cut off the old plug and splice in a new one if you can find one (wreckers or see if it's available new) just to be sure you're done with this. Ford made a run of alternators that had a similar problem. The rocket surgeons decided to use two thin wires instead of a charge cable, and spade terminals in a plug rather than the usual stud and nut arrangement. Cost cutting, I guess. The spades corrode, the plug melts, and the whole mess catches fire.

It's not really a fuel reserve, it's just fuel the pump can't get to. The fuel pickup isn't quite at the bottom of the tank, it's a flat-bottomed tank, and it's fairly wide, so the pump runs dry before the tank is properly empty. My WD21's the same way. It's a 21 gallon tank, but it can only use maybe 16 of that. +1 for the locked up fan, that's not helping your MPG. If it's still low after that, start checking sensors. I'd hazard a guess at a temp sensor or primary oxygen sensor, but I don't know the VQ very well.

This is turning into quite the rabbit hole! So it wasn't the through-hole cap. What about the two surface-mount caps on that same board?

Yeah, that's not good. I'm not familiar enough with the R50 wiring to know where ignition 1 goes. You can check the EL section of the service manual to try and figure out where it goes (by color if nothing else). (I don't know where to get a full diagram for the R50, unfortunately, so you'll have to work with the partial diagrams Nissan apparently thought their techs would need.) Something on that circuit is clearly drawing way too much power, but is somehow not blowing a fuse. What I'd do is try and figure out what all is on that circuit, start unplugging things (or pulling fuses or fuse links, though, again, I'd expect the fuse to melt long before the ignition switch did) until you can turn the power on without that wire heating up. Then investigate the last thing you unplugged. Also, if you had some part of the truck apart recently (particularly dashboard or engine bay), check your work there first in case something got nicked or pinched where you were working. Good luck! Electrical issues can be a real PITA.

Huh. I didn't know the R50s dimmed their dome lights, that's unhelpful. And yeah, a cap is probably the way to deal with that. A cap across the relay coil and a diode to isolate it from the rest of the circuit would make sure the cap was keeping just the relay energized and not dumping its power through the dome light bulbs or possibly confusing some other part of the circuit. I did something similar when I wired a lighted ignition cylinder ring off my dome light circuit. I wanted the ring to stay on briefly after the door was closed (because otherwise what's the point), but I didn't want the dome light to stay on. I wired a couple of capacitors to the LEDs on the ring and ran power from the dome light circuit through a diode, preventing the caps from discharging through the dome and footwell lights.

This is probably to prevent the tire from blocking view of the right side tail light if the driver behind is following closely or passing.

If it's tight and clean, it won't need wiggling around to keep working. You can get terminal cleaner brushes for cheap that'll clean the inside of the terminal and the outside of the battery post. Get it cleaned up, tighten it down, and it should be good to go.

My opinion of my truck also changes depending on whether I'm driving it or working on it. Nice work on the diff drop! I saw a kit a while back that had bushings with the inner sleeves off-center. No welding, but if you didn't clock them perfectly, they'd be a huge PITA to get the bolts through. I like your way better. Consider preemptively replacing the bushings if you pull the brackets again, IIRC a couple guys have had weird front end rumbles turn out to be dead front diff bushings. Looking at how little rubber's actually in that bushing, I think I know why, too!

The computer doesn't really need an idle sensor--it's watching engine speed anyway. There is a pressure switch on the power steering and some kind of tie-in from the aircon that tell the computer to raise the idle when those systems are under load, which might explain why Adam's aircon masked his idle issue. Idle control is done by two valves. The Auxiliary Air Control valve (which the computer controls) is located under the back of the upper intake manifold. The Idle Air Control Valve, which lets air bypass the AAC for a higher idle when the engine is cold, sticks up behind the EGR and works kind of like an electric choke (moves a valve as it heats up, only instead of opening a choke, it closes an air passage). EF&EC-14 of the '95 manual has a picture and description of each. (It also shows the AAC and idle adjustment screw together and calls the pair something else, just to be confusing.) The IACV is only open when cold, which is when your truck runs its worst, right? The idle control components do one thing, and that's feed air into the manifold, bypassing the throttle body. That air is supposed to come from the intake tube between the MAF and the throttle body, meaning it's gone through the MAF already, so the computer knows it's there (and knows to add fuel accordingly). If the idle control valves are drawing air that hasn't gone through the MAF--air getting into that feed pipe through a crack or a hole where a mouse chewed on it, maybe--the computer isn't seeing that air, and doesn't know to add fuel, so the engine will run lean. It would run leanest when the IACV is open (when it's cold). Once the IACV closes, the engine would idle better, but still a little lean from the lower volume of air going through the AAC valve (low idle). When your foot's on the gas, the AAC should be closed, and the engine should run closer to normal (though perhaps not perfect given that the leak that was supplying unmetered air to the idle controls might also send some the other way to the throttle body). So, yeah, I'd have a look at that air supply pipe. As for the EGR, I haven't heard of any real benefit to deleting it unless the valve is buggered. Mine works, so I leave it alone, though I did scrape some carbon buildup out of it when I had the intake apart and test it just to see if it was working right.

I doubt you'll find the original brackets, but there's a diagram showing where it all attached to the exhaust in the FE section of the service manual. Looks like most of them wouldn't help you anyway unless you also tracked down the factory exhaust pipes with their bolt flanges and mounting points. I'd be inclined to make something work with U-bolt clamps if you don't want to weld directly to the pipe. What brand was your last system? Even in salt country three years seems pretty short-lived.

Hmm. Yeah, seems like it would run like ass all the time, though maybe it would be more obvious when cold. You can pull the vac line off the valve and see if the engine runs any different (the valve should close if it's being held open by vacuum), then either apply vacuum with a pump or reach underneath and push the diaphragm (probably best to do that with the engine cold) and see if the engine stumbles when the valve opens, or if it doesn't change from the stumbling it's doing already. The EGR control solenoid was jammed wide open on my dad's '87 F150 and it ran like crap until I tracked it down. On that one I unbolted the valve and put it back with a piece of cardboard in between it and the manifold, sealing off the hole, and when it ran better like that I knew the EGR was at least part of the problem. IIRC it ran a little better when warm, but it never really ran right.

Given what you've done already, I'm not sure what would make sense to do next--though I'd still be suspicious of the temp sensor. When it's running like crap, can you tell it it's running rich? Lean? Misfiring? The plugs might give you an idea of what you're up against and whether it's the whole engine running weird or just one hole. I'm guessing it's got no codes at this point, just to be like that. I'd also check the EGR valve on the off chance it's jammed itself open, or the EGRC solenoid's given up.

In theory the CVT is a great idea. You can keep the engine in its torque band all the time. Go-kart guys love them. From what I've heard/read, though, vehicles with computer-controlled CVTs tend to be useless. A friend of the family has a newer CRV that can't get out of her driveway in the winter. I don't know if it's just over-cautious traction control (my mom's '07 had a normal slushbox and just gave up if it thought the wheels were slipping too much) or if the computer can't figure out where to set the ratio with inconsistent wheel speed and gives up because of that. Also, yeah, I haven't heard much good about their reliability.

Haven't heard of that trick before!

Weird. There's no mention of a California-spec exhaust in the service manual. I had a look at the diagram on factorynissanparts for the '99 system (figured VG vs VQ might be different) and it shows different year ranges on some parts for California/federal, and different three-way cats up by the manifolds for California/federal, but I don't see any secondary cats listed. The Courtesy Parts listing for the '04 resonator linked above says it says it fits all US-market trucks from January of 2000 and up. The only mention of California is that it causes cancer there. (I couldn't find a similar part for earlier trucks, but I didn't search that hard, either.) I would not be shocked if the service manual forgot to note something important, but I'd expect the parts sellers to at least note that the parts existed. I can't explain what OSB saw, though. OSB, where are you finding the info on the CA variant? Looks like the R51 has front and rear cats, for what that's worth. I also remember the guy who replaced the exhaust on my '95 saying it had two cats under it for some reason, but I don't remember anything about that myself; it was a long time ago and I wasn't quite as inclined to dive into Pathfinder-related rabbit holes at the time. It's entirely possible he mistook the big Y-pipe junction or something for a cat.

Sounds like there is a pilot bushing in the crank for the auto trans. I'll second the grease trick mentioned there, it worked to get the roached pilot bearing out of the 302 that's going in my dad's hot rod. We used a socket and an extender to get the right size to fit the bushing, and some bits of paper towel to take up space so we didn't waste as much grease (and to prevent the grease squeezing out around the socket). Apparently soap and even bread can be substituted for the grease. Apparently there's an oil passage plug behind the pilot, so be careful not to beat on the crank itself.