Slartibartfast

Weird. The only way I can imagine the heater making the engine shut off is if the heater and the computer share a power or ground somewhere that's getting weak and can't handle them both, but I'd expect that to cause problems as soon as you turned the heater on, not 10-15 minutes later. Any pattern to when it craps out? At stop lights, under load? Any other symptoms?

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I'm not familiar with the cooling system of the R50 (and I don't even know which engine a TI would have), but with the recent work, I'd start by checking the clamps on the hoses. Could be something was just left a little loose. If you can see a hose from above, feel around underneath it; if it's leaking at an end, the coolant will run down to the bottom of it, so you may not see anything from above.

When the trans went out in my friend's Blazer, we drilled a hole in the pan to drain it rather than wrestle a full pan around the exhaust and probably spill it from hell to breakfast. We also added a drain plug to the new pan just in case we ever had to mess with it again. Drain plugs are good. I flushed mine through the cooler lines (just stuck them in a bucket and ran it until it quit pumping fluid out, refilled, did it again, until the fluid coming out looked fresh), but did end up losing track of how much I'd put in vs taken out and ended up having to drain about a quart to get the level right. The level changes as the trans warms up, which can make it interesting to set and easy to overfill.

Probably the easiest way to do it would be unplugging the door lock timer behind the driver's side interior panel in the cargo bay. Little plastic box, labelled Door Lock Timer. The solder joints inside tend to crack and cause weird lock behavior.

I flushed mine myself using the cooler lines. Unhook, put them in a bucket, run the engine until it stops puking fluid, add the same amount of fluid via the dipstick tube, run again, repeat until the fluid coming out looks more like the fluid you're putting in. Mine was brown and had a little sparkle to it when I first disconnected the lines, which isn't a great sign, but not shocking on a truck with 200k+. I hooked it back up with an external cooler in line with the stock one (new-ish radiator so I'm not worried about it) and a Magnefine in-line filter to hopefully trap any remaining wear material. I used generic dex/merc ATF and ended up draining a little back out using the pan plug after adding about a quart too much (it can be tricky to get the level correct). I've never seen my AT temp light come on, +1 for checking wiring if it's on all the time. I've got a paper copy of the '87 service manual, so let me know if you need specific info. Most things are similar to the later trucks, but there are a few curveballs in there, including the engine diagnostic codes (same procedure but they switched a few numbers around, just to be that way). Also IIRC the '87 was the only year that used a three-speed automatic, so if it does end up needing a trans at some point, you may be in for a scavenger hunt to find the parts you need.

EL section of the '95 manual should have what you need.

Sounds like the speed sensor has quit and the trans computer is trying to tell you about it via the old blinky-lights OBD carried over from earlier models. AT-45 of the '98 manual has the procedure for decoding what it's unhappy about by watching for a longer flash. Looks like each code has its own page reference for further troubleshooting as well. If you don't get anywhere with the blinky lights, and you have an OBD-II scanner, give that a go. Looks like most of the patterns listed also have a DTC associated with them. I don't know whether a cheap code scanner would see codes on the trans computer, or if the DTC numbers mean they'd show up on the engine computer. Won't hurt anything to try.

What change did you see after adding this stuff? Was it having issues before?

You could go through the filler with a hose if all you're doing is pumping out the old gas, just watch out for the anti-splash whatsit (hinged bit of the filler that the gas pump nozzle pushes aside, it likes to get caught on things). For that matter you could just unhook the fuel filter outlet, put a piece of hose on that, and run the truck's fuel pump to transfer most of what's in the tank into a bucket. Personally I'd want to go for the pump so I could inspect it and the inside of the tank to make sure there isn't crap in there waiting to cause fuel system issues later, but getting the pump out and in again does involve some screwing around. There's an access panel under the carpet, but to get the carpet up, you'll need to remove the rear trim plate (plastic phillips screws that like to slip, best to use a small flathead with as little downward pressure as you can and get a fingernail under the screw head to keep it from slipping back in) and the cargo tie-downs (big Phillips bolts through the floor, I replaced mine with 10mm hex bolts after how much fun the Phillips heads were to remove). I hear you on not wanting to drop the tank, it was no fun at all on my '95, mostly because every fastener on that truck was rusted in place.

+1 on checking the brakes. The fuel would by my main concern before trying to start it. I'd pull the pump and look inside and see how much crap you're dealing with, and decide from there if it's worth dropping the tank to clean or if you can just drain, fill, and send it. Might save you some future issues with clogged pickups/filters/etc. Might as replace the fuel filter while you're at it. Hopefully it's not too bad. My dad and I pulled a tank from a Jeep that had sat outside for about 14 years with a tank of ethanol gas, which had turned into some kind of caustic schmoo that looked like bear crap, moved like taffy, and had eaten a bunch of holes in the tank. Hopefully better conditions and less elapsed time were kinder to yours. Do you know when the timing belt was done last? They have a mileage interval, but time kills rubber too. Unless the belt was getting close to retirement when you parked it, it's probably fine for a first start, but I'd want to replace that before putting miles on it. Not a bad idea to clean out your heater box, too, on the off chance something's taken up residence in there. Welcome back and good luck!

I'm not usually a fan of tuner rims on these, but damn that looks good.

Time to take it off the road until that's fixed. Ain't nobody got time for the rear end locking up at highway speed.

I don't know what would cause that, but it doesn't sound good. The AT Section of the service manual should have some kind of troubleshooting info for that code. Good luck!

I've got Mile Markers on my '93. McBay Performance (online) had the best price at the time. No complaints mechanically but their chrome sucks, most of it has blistered and peeled off the aluminum trim rings. The dials still look alright. I had to modify the hubcaps a little to clear them, I don't remember if the R50 wheels require similar treatment. They were a huge upgrade from my crap-tastic worn-out auto hubs. Your drive flanges are at least reliable, so you may not get as much benefit for the money as I did. Whether it's worth it depends on how you use the truck and what other mods you're planning to do in the future. And yeah, the only real downside is having to get out to engage them. I leave mine locked all winter, so this is only a problem if I get into something I didn't expect during the other half of the year. Even then it's not really an issue unless you're bogged to the frame in pig crap and the pigs have you surrounded.

The temp gauge in my '93 doesn't go to the center, either. The heater's no face-melter, but it's adequate. If the coolant was manky, you may need to flush the heater core. I don't let mine sit and warm up much unless it's single-digits cold out, and it's usually warm by the time I've driven the four highway miles into town. And yes, you can run it without the fan. If you remove the whole fan assembly (blades and clutch), make sure you've got something else holding the pulley to the water pump. #4 being darker than the rest could suggest a leaking injector, which would explain the foul smell and lousy fuel economy. If all you've done doesn't improve how it's running, pull the plugs again and see if #4 still looks richer than the rest, or if it smells like gas. +1 on the oxygen sensor. These use primitive old-school oxygen sensors that pretty much just read "rich" or "lean." When the ECU's in closed loop, it adds fuel if the sensor reads lean, and reduces fuel if it reads rich, bouncing the ratio back and forth across where it should be. The sensor can slow down as it gets old, meaning the mixture strays farther from ideal before correcting. There's a test mode for the ECU (EF&EC section of the manual) that lets you monitor how fast the sensor's switching back and forth. The sensor can also fail entirely and make the computer see a lean condition regardless of what's actually going on, which will make the computer add more and more fuel as it tries to compensate. A fault with the oxygen sensor or the coolant temp sensor would cause an issue across all six cylinders, though, not just the one. I'm happy to hit 16 mpg in mixed driving. I've seen 19 on long flat highway trips. But I have also seen 12-13, especially in the winter. Short trips, locked hubs, screwing around in the snow, that kind of stuff's hard on fuel economy. Add yours running rich and the 15-minute warmups and I'd be surprised if it didn't get lousy fuel economy. Still, at its best, my Pathfinder's mileage is about on par with my dad's V8 Tundra, which is depressing given how much get-up-and-go the Tundra has that the Pathfinder doesn't.

The clutch fan doesn't really cycle. If you have the push-button HVAC, you may be hearing the aircon compressor cycling (the aircon kicks on in defrost mode to act as a dehumidifier). If the engine is staying cold, the EFI may not be going into closed loop, which would explain the lousy mileage. Thermostat's my first guess too. My temp gauge seldom goes past half way but certainly more than 1/4. When you swap the coolant, make sure to bleed it. There's a bolt on the upper intake plenum (towards the back, on top, marked "do not open when hot"). Fill the system from the rad, put the cap back on, take that bolt out, and squeeze the upper rad hose until coolant comes up to the hole. Then, while holding the hose, put the bolt back in and snug it up. Then take the cap back off and top up as needed.

That's funny. I didn't know the WD21's blinking light engine diagnostics continued into the R50.

The more you describe it, the less it sounds like anything drivetrain related. Can you get a video of the noise it's making? Might help for tracking it down. Any other known issues?

I think I saw a writeup of someone replacing the chain. Didn't look too complicated, but it's probably cheaper and easier to find a good transfer at the wreckers and swap the whole thing if it comes to that.

What I'd do is drive in a slow tight circle, on dirt, in 4x. That should put some load on the front end. If everything's working right, the wheels should just scrub a little. If you get the thudding/banging noise instead, you could have a stretched/slipping transfer case chain, or maybe a CV joint popping. If that was the issue, though, I'd expect it to make the noise any time it was under load, not just a single thud after 5-10 minutes of wheeling, unless your trails are easy enough that you don't need to be in 4x to begin with. If you can't make the drivetrain make the noise, maybe something's just loose. Check the U joints for play, make sure the trans mount is in good shape and bolted in properly (sounds stupid but the trans mount on my friend's van was just sitting on the crossmember when he got it). Might check the front diff mounts too, I think a couple of the R50 guys have had those go bad and let the diff flop around. Could even be a suspension issue, something loose that only acts up when the suspension's flexing off-road. Bricknose Ford trucks tend to have weird popping noises when the frame cracks near the steering box, never heard of one of these doing that though. I read a story a while back about a car that had a clunk noise that nobody could track down. It only did it when it was freezing out. Brand new car. They replaced bushings, tore all kinds of stuff apart, couldn't find it. Later someone went to replace a smushed fender and found a condom full of water hanging behind it, with a note that said "how long did it take to find this?"

That's quite a patch! And yeah, the shoulder belt buckles go in the two inner holes, by the seat back bracket you've got your ground clamp on. Don't mind the walnut grit and the I-can't-believe-it's-not-dynamat.

Nissan Nut did a writeup on alt upgrades. It's specific to WD21/WD22, so the mounting info won't help you, but the alts he calls out might. Also consider upgrading your charge cable at the same time. It's probably sized for the alt you have, not the alt you want. I know the charge lead on my '93 (70A alt) is pretty tiny. Whether you need a bigger alt depends on how much you try and run at once. Unless you're planning to run face-melting bass and a small waffle iron at the same time, you may be alright with what you've got. I'd say install your accessories, see how the charging system handles them, and upgrade from there as needed. You can use a simple relay setup to control a second battery. IIRC somebody rigged theirs to an oil pressure switch, not the key switch, so it wouldn't charge the second battery until the engine was running (so a flat second battery won't sap power from the starter motor). It's a simple system, but kind of brutal to the second battery. You can get proper charge controllers that may make the second battery last longer, but they're not cheap. Lots of research to do there if you're looking for a rabbit hole to fall into.

Too dark for a decent pic at the moment (and too much junk in the back). I'm guessing you took the belts out and are trying to figure out where they went? Mine's got the reel for the center belt on the passenger's side, the two side belt buckles in the middle, and then the center belt buckle closest to the driver's side. I assume this is correct, couldn't find anything in the service manual to confirm though. If you still need a pic let me know and I'll try and get one when it's light out.

Yeah, that could explain the debris. You could just grab a third member from the wreckers, easier to replace the center than the whole axle. The '00-'01 Xterra LSD is supposed to be better than the R50 LSD if you can find it, might be a good excuse to upgrade.