Slartibartfast

Stuck valve doesn't make much sense with the compression reading good. Dieseling sounds like an injector leak. Not sure how an injector leak would cause a single-cylinder misfire, though.

Ick. Good thing you checked!

Nice of it to give up in a parking lot, rather than on the road! Score! I'm still using my great grandfather's vice. Don't think it built any battleships but it kinda looks like it took a shot from one LOL.

Hmm. TBI, so it's not a dead injector. Assuming all tests so far are accurate, and all parts replaced are good, all I can think of is a restriction in the intake or exhaust runner for #5--like the air cleaner was off and a mouse crawled into it or something like that. (How's that for a long shot?) Could try positioning the engine with the intake valve open, spark plug out, and jam an air nozzle in the hole to see if anything blows out.

I tested connections on mine before soldering by undoing the amps and using short lengths of wire and the legs on the capacitors to jumper the pins in the plug as needed, just like using a breadboard. Worked fine for a test. I'll bet if the wires fit well enough into the plug, you could just wrap the whole SOB in tape to hold it together and call that good. Or, you know, learn to solder. Really comes in handy working on cars.

The trans going into limp mode is likely connected to the malfunctioning speedo. The auto trans uses the speed sensor signal to decide when to shift, so a failing sensor or damaged wiring might be causing both issues. The temp gauge is connected to a temp sensor on the coolant neck (the one with a single wire, the two-wire one is for the ECU). Check resistance from that spade terminal to ground with a meter, I think there's a spec in the service manual for what it's supposed to be at various temperatures. If the sensor's buggered, the temp gauge could be an easy fix. When I got my '93, the terminal was loose where it was riveted to the sensor, and the gauge hardly moved at all. Swapped in a good used one (not that they're hard to find new, I just had one handy) and all is well.

The trouble with the stock stereo is that Nissan, for whatever reason, used a head unit that outputs to a pair of amplifiers (should both be in the passenger's rear quarter panel on your '95, that's where mine were anyway), and those amps are what drive the speakers. Hooking up a new HU to the old HU outputs can be done if you also connect the turn-on wire for the amps, but I don't recommend it--your HU will have to be on low volume to compensate for the amps bumping it up and any stupid beeping noises your HU makes will be deafening. Better to bypass the amps. I did a writeup on this a few years ago but of course the pictures are gone because Photobucket. The Crutchfield chart (linked in the writeup) is most of what you need to know anyway. The other way to do it is to just run new wires from your aftermarket HU directly to the speakers. The stock wires are pretty thin and much longer than they need to be. This is probably the better way to do it, but my dirty/quick/nasty worked pretty well, too. Oh, and the stock amps aren't completely useless, either. I wired a 3.5mm jack to my old rear amp (just hooked it to the right/left inputs and ground) and connected it to a couple speakers and ran that in Rat Trap for quite a while before I got around to installing a new stereo. Also makes a good shop stereo, if you've got a 12v supply handy.

Sounds like that's your problem right there. The computer decides how much fuel to spray depending on how much air it thinks the engine's pulling in. Any air leak downstream of the mass air flow sensor (on the air filter box) is letting in air that the computer doesn't know about and leaning out your mixture. Fix that busted elbow and the truck should be a whole lot happier. And yeah, you have to let it warm up before setting timing.

Cool idea! I've considered getting a white one and painting the "Me Gusta" meme face on the back, just to worry people.

Check if it takes a standard key or a chip key. I haven't messed with this myself but I've read that Nissan got into the chip key racket in '99.

If the computer thinks there's something wrong, it can limit RPM to 3k (or it can on the WD21s, I assume R50s are similar). If the timing is correct, my guess is that the knock sensor's seeing preignition caused by a lean mixture. Pull a plug, see if it's white on the end, and check your vacuum hoses and rubber intake pipe for cracks and dry rot.

Gained respect for its design and construction by working on a Ford.

Jesus, that's ridiculous. I spent, like, $50 on generic dex/merc for mine and IIRC had enough left to do the transfer case. And yes, the transmission cooler built into the rad on the R51 tends to break and let coolant in! Good thing to bypass and run an external instead; the cooler in front of the rad is a much better bet (and if it sprung a leak, no, condensation wouldn't get in; tranny fluid would get out).

I doubt it's necessary but it couldn't hurt.

1" should be fine. IIRC you can get away with about 2" before the upper ball joints get unhappy.

I didn't set mine like that either--couldn't be arsed to find the exact shim and weight and all that. I went by the procedure in this writeup and it's gone 9k so far without issue.

Zed put Mustang seats in his and seemed pretty happy with them. Of course the pictures are dead because Photobucket but it sounds like an easy enough process. I haven't messed with mine much but I need to open up the driver's seat sooner or later to either fix the seam that's failing or swap for something else.

How's the surface the seal rides on?

+1 on the trans cooler. If you really want to play it safe, you could install a trans fluid temp gauge as well for an early warning if you're driving it too hard. Shift points are determined by engine speed and load. The AT section of the WD21 manual has a chart for when it'll shift charted against throttle position and speed. If you're just barely on the throttle, it'll go for second at around 10 mph, third at maybe 15, and overdrive in the low 30s. If your foot's to the floor, it'll hold each gear to redline, holding first to 30, second to almost 60, and hitting overdrive in the high 90s. (The R51 manual may have a similar table, if it's not all instructions for playing with the scan tool.) You can watch the tach while you drive an auto to see this in action, and it may help you get a feel for where to shift manually if you decide to give that a go. If the R51 gives you an option to turn overdrive off, do it. Overdrive's a pain in the ass when you're struggling for power. I turn mine off in my WD21 any time hills are involved, even if I'm not towing; otherwise it tends to go for overdrive when I lift for a corner and then struggle when I get back on it because it can't climb a hill in OD and apparently nobody ever bothered to tell it that. Assuming Nissan did a better job programming the R51's trans than they did on the WD21, O/D off may be all you need. If you notice the computer's holding it in too high a gear (low revs and struggling to maintain speed), or hunting like Boothill said, consider using the manual mode to lock it in a lower gear where the engine can hold enough revs to keep you going. I've heard some trailers handle better with empty water tanks (less weight behind the rear axle)--might be something to consider if you can fill up when you get there.

Easier fix than a chowdered keyway! Also good you caught it before it came apart.

(edit timed out) Looking through that Infamous thread again, it looks like the curse of Photobucket struck there too and took out the pictures I built mine from. If you want to go that route, PM me, I probably still have the schematic saved somewhere.

I've seen OBD1 to OBD2 adapters offered for other EFI systems, even for Nissans, but I've never seen one with an end that looks like it would fit the connector in a WD21. I don't think the ECU in these is even capable of talking to a reader. This writeup is for a different Nissan but have a look at the FSM excerpt at the end to see what Nissan's code checker box looked like--just a box with two lights, a button, and a buzzer in case you didn't want to look at the lights. I built a similar device from schematics somewhere in (or linked from, don't remember exactly) this thread on Infamous and mounted it to my dashboard so that I can run codes or monitor the O2 sensor or whatever from the driver's seat rather than screwing around with the ECU directly. It's still just flashing lights, though. If you're good with coding, and bored, you could probably rig up some kind of arduino decoder that would run the ECU through its test modes, collect the data, and look up the codes for you. You're never gonna get the functionality of a modern OBD2 out of it, though.

And you're sure it's the PS?

Ah, makes sense. It seems to be a rare enough issue that I'm not too worried, but I'll certainly check for play the next time I've got the wheels off.

I've seen pictures of LED conversions on here so I know people have done it. Hopefully one of them can tell you what they used. I like LEDs generally but most of the LED-swapped clusters I see have really bad hot spots (probably something to do with the beam angle--I'd assume the wider the better for general illumination). That, and a friend of mine fitted the cluster his Chevy with the cheapest LEDs he could find, and after awhile a couple of the chips went bad and started flickering. Decent chips with a wider angle might give better results.