Slartibartfast

I'd have a look at the ground wires for the tail/brake lights. The two filaments share a ground, which isn't a problem normally, but take away that ground and those two filaments form a bridge between your brake light circuit and your markers. I'd take out one tail light bulb, see if that made the problem go away, and if not, put it back and try the other. That should narrow down which side you're up against. If the ground point isn't obvious inside the fender (never looked for it so I don't know) I'd check the EL section of the manual to try and work out where the wire goes.

http://www.nicoclub.com/FSM/Pathfinder/Download the '95 manual and look in the LC section. A mechanic I know told me he's had trouble with those T-fittings getting brittle. A friend of mine used one on his van with no issues so far. I can see using it on the van (where the working room in the engine bay is a cruel joke at the owner's expense) but I'm not sure I understand the benefits of it otherwise.

Huh? Limp mode locks the trans in third gear. That is not normal, no matter how cold. Looking at the manual, is it possible that what it's actually showing is the on/off pattern on AT-41? Looks like a reversed battery, low voltage, or a long time without voltage will make it just blink at you (and it doesn't say how many times it'll do it). The "long time without voltage" is interesting to me. It looks like the TCU has two power feeds running through the fuse box, one switched with the ignition and one not, so the one that's not is probably how the unit remembers if it has a stored code or something. If it's not getting power on this line, it might trigger the "battery has been disconnected for a long time" error when the ignition switched line powers it on again. Then when you shut off/restart, if you're quick about it, there could be a capacitor or something inside the TCU that keeps it alive for the moment that power is disconnected. AT-37 shows the location of the fuses in the box (you could check for power at the plug for the TCU as well). This is a shot in the dark, of course, I have no idea if that fault is enough to trigger limp mode.

I'm guessing this crossmember looking deal at the bottom of the picture is the rear mounting member you're looking for. I've read that you can get the engine around the diff if you disconnect the trans and get it out of the way first, but that was with the VG30--I don't know how the sump shape/depth compares. image poached from here

Checked mine and yeah, 4815 StrongArm. This is the second rig I've had this same set bolted to and they still look new.

Reminds me of the mess I found behind mine. I'm not sure the antenna lead is even in there anymore!

Looks like EL-204 of the '03 manual shows a red wire going from the "audio unit" to the power antenna. Not sure if that's the same for 2000, but easy to check the manual.

No idea on part number but I think I got mine from Rockauto a few years ago. Pretty cheap and they still work.

Yep, sounds like the brake light and tail light circuits have come together somewhere. Check the bulbs, check the trailer harness if you have one, might've picked up some mud or something.

Glad that's what you were after! I was able to get to the plugs pretty easily, but I didn't check access for the fasteners. Hopefully there isn't too much junk between you and it.

And replacing it didn't change anything?

The manual says it should read around 2.3-2.7k at 68° F, .77-.87k at 112° F, down to .33-.30k at 176°F. I'm assuming NY is colder than 68° right now, so you'll see a higher resistance than 2.7k, but 5.94k does sound suspiciously high. If you want confirmation, you could pull the sensor, warm it up in a cup of hot water, then check it with the meter again.

I'm not entirely sure what part you're after. I don't see anything by that name in the circuit diagrams. Couple shots in the dark though: The fan speed control is done by four separate relays. Two are above the driver's footwell towards the right, the other two are nearby just enough behind the center dash plastic to make them hard to get at. They're the standard blue relays and three of the four are marked with colored tape around the wires so you know which one is which. Definitely not a 3x3" black box though. 12, 13, 14, and 15A on HA-62. There is a black box on the right hand wall of the driver's footwell that the manual calls the auto amp. It's closer to 4" square though so it might not be what you're after. 4A on HA-62. If that doesn't help, let me know, I have a full working (near as I can tell) auto hvac system in my rig I can take a closer look at.

Stupid question on the cover. Would it be more work to stick with the original cover and just buzz off the mount vs modding the flange on the other cover?

Interesting that unplugging the TPS got it running (sort of) better. The TPS is what tells the computer when it's supposed to make the engine idle, so if that's broken, it could be telling the ECU to idle all the time. You get on the gas, the engine revs way above what it should do at idle, and the ECU panics and cuts spark or injector pulse to bring it back down. With the sensor unplugged, the computer doesn't know when the engine's supposed to idle, so it's not adjusting the idle air control valve or doing any of what it's supposed to do there, which would explain the rough idle. I don't know for sure but I suspect its response would be to throw more fuel at the problem, which would explain why your mileage got worse. I would start with the TPS. Keep in mind that there's a little adjustment to it as well; if you or someone else had it off just before the problem started, it might just need adjustment. I haven't messed with mine but the service manual (here, download the '94 or '95 manual and look in the EF&EC section) should walk you through it. I would probably just hook a multimeter to the closed throttle position switch and adjust it so the points close when the throttle's shut.

Sounds like you've got a hell of a misfire that only pops up under load, and only when the engine is cold. That's not ringing any bells for me, but I'd start by checking the vac lines (especially the one to the fuel pressure regulator), checking for any ECU codes, and maybe doing an ohms check on the temperature sensor as well.

AT section of the manual: http://www.nicoclub.com/FSM/Pathfinder/

Definitely sounding like an intermittent electrical problem. No thermostat would keep it from warming up/make it run rich all the time but I can't imagine how it would prevent the engine from starting.

No drain plug. The last time I had to drop a tank, I ran the truck almost out of gas, dropped the tank out, then poured it into a bucket. Easier to just pull the pump out and see how it looks in there.

I hear you on the new part costing more than the truck's worth. My dad's '03 had massive oil consumption and it was the same story with the engine. Not worth the cost of the shop time to dig into it to find the problem, let alone to fix it. I wanted to tear it apart myself but it was his daily and it still ran, so he just added oil until he sold it. Trouble is, I'm pretty sure the R51s are on CANBUS. Some rigs have an aftermarket solution for engine swaps, but aftermarket for Nissan trucks has never been great, so I think you'd be on your own for getting the CANBUS systems back online after getting the Chevy running gear into it. A fun project if you're into that sort of thing (I don't even want to be in the same room with that can of worms), but I'm guessing your daughter wants it back on the road at some point in the near future. Probably more realistic to find a trans at the junkyard (look for a wrecked donor, the problem's common enough that I wouldn't trust a trans from a rig with no obvious reason for being there), flush the strawberry milkshake out of your cooler lines, get an aftermarket radiator that wasn't designed by accountants, slam the SOB back together and get it out the door. And then find something more fun to put your 350 in.

Not sure about the other models but I'd be real surprised if it was different from the D21.

Alright, so clearly not the filter. The symptoms aren't ringing any bells for me, but you might want to have a look at the fusible links hanging off your positive battery clamp if you haven't already.

AFAIK there's no set rebuild interval on these. Probably depends more on how it was treated than on the odometer reading, and I don't have the hands-on with this box to really say more than that. Might give this a read-through as well, to get an idea of what you (or the guy installing the trans for you) is in for: Edit: This might shed some light on what to look out for.

The service manual. First off, do you know if/when the timing belt has been done? At 95k your rig is closing in on the change interval for the original belt, and if that belt is 21 years old, I wouldn't trust it very far. If you remove the distributor cap and turn the motor over, and the rotor doesn't spin, your belt has packed it in. Hopefully it's not that. Speaking of the distributor, when you removed the manifold, did you remove the distributor as well? Are you sure it went back in with the rotor facing the right way? Smelling gas isn't uncommon on these. There are a couple of rubber lines connecting the fuel rails at the front of the motor, and I don't know if the rubber shrinks or the clamps work loose (or both), but that's where they usually leak. Tighten them up and that should deal with the leak. The click at the bottom of the gas pedal travel is normal, that's the switch that tells the trans you're standing on it and it should downshift. Not sure about the loose feel, maybe make the throttle cable is hooked up properly, and make sure the throttle is moving when you move the pedal (checking for a broken cable). Wouldn't explain the no-start but easy enough to check.

Replacing the fuel filter is a good idea, and it's easy, but I wouldn't be surprised if it didn't solve the issue--I wouldn't expect a clogged filter to be intermittent, and I wouldn't expect the engine to run well when it did start. This sounds more like an electrical fault to me. When it's cranking but not starting, can you hear the fuel pump running?