Slartibartfast

+1 for checking connectors and giving the computer a time out. I've got a loose MAF plug on my MPFI that makes it surge and stall when it acts up. I would also re-check the vacuum lines around where you were working. I have not worked with the TBI, but I've heard it can be pretty finicky, including running poorly with the air cleaner off. I don't have a PDF of the '87 manual, but I've got a PDF of the '89 up on Dropbox, and the TBI system is the same between those years AFAIK with the exception of some codes that got moved to different numbers, just to be difficult. (The '87 lists 42 as TPS, 43 as injector circuit, and 44 as no malfunction; all the other manuals I've got lists 43 as TPS, 51 as injector circuit, and 55 as no malfunction. The coolant temp sensor code did not change, so, no worries there.) The EF&EC section of that manual can tell you more about the TBI than I can. If you run into something in the '89 manual that doesn't match what you're seeing, message me, I've got a paper copy of the '87 and can cross-check if you want.

You won't know how bad it is (or isn't) until you get that tape off.

I would expect it to throw a check engine light sooner or later.

Sounds like you've tracked it down. I wouldn't expect a reed switch to fail intermittently, but maybe something came loose inside, or the contacts fouled. The contacts opening and closing might've worn through the fouling a few times before it stuck for good. Might also be the drive gear is missing a couple teeth, and sometimes it stopped in just the right place to where it wasn't driven. Hopefully you don't get it apart and then have to go track down a gear. The sensor pulling a 5v line to ground sounds reasonable to me. Could also be that the cluster or engine computer modifies the sensor signal in some way before sending it on to the transmission computer. I have no idea if those connections are straight through or not. Not sure on the fluid. Find the fill hole for the transfer and see if it's higher or lower than the speed sensor. If it's lower, then yes, you'll have some ATF come out to say hello.

Looks like the smaller of the red wires coming off the + terminal goes down to that wad of electrical tape, which I'm guessing is where it connects to whatever is left of the fuse links. I see a plug behind the battery there which is probably related. I also see a white wire cut off and just sticking up next to the steering res. Get the battery out of your way so you can unwrap that tape and see what kind of mess you're working with--and if it's not as bad as the wad of tape leads me to believe, find and check the fuse links, assuming they're still down there. When I replaced the + terminal on mine, I adapted the fuse link connection to the new terminal with a short copper bar. Bolts to the terminal on one end, bolts to the connector for the fuse links on the other. I assume the cable was used for the same purpose. Looking at mine again reminded me that most (?) of the links are short lengths of wire between two plugs, not loops from one plug. Worth noting, the wiring for the adjustable shocks is part of the starter harness and IIRC it goes right past the battery there, so don't go connecting wires just because they're there--make sure you know what they are first. Off the top of my head I think the adjustable shock wires are white with colored stripes, but it's been a while since I tore those out of mine. Again, the EL section is your friend. I'm also curious why one ground lead goes to the bolt it's supposed to be on, while the other one is on the clamp bolt, sitting all cockeyed. I don't think that's why it's acting up, but it ain't right.

It sounds like it's in limp mode. Exhaust getting that hot is probably due to the misfire (unburned air/fuel mix hits the catalyst and burns there instead). First thing to do is run trouble codes, see what the computer thinks is wrong. If that gives you a cylinder-specific misfire, figure out why that cylinder isn't hitting. If it's not cylinder-specific, could be mixture. Check the rubber tube between the MAF and the throttle body.

I read that as "change the oil more often if you're stressing the drivetrain." An empty roof rack should not be stressing the drivetrain.

The mechanic may not have thought to look for fuse links, or recognized our old-school fuse links when he saw them. If you don't find something obviously/visibly wrong, turn the key on, blower to full, and wiggle wires on the + terminal until you find one that makes the blower kick on. Might show you where the problem is if it's just a weak connection.

It's not the computer. The circuits that are acting up are not computer-controlled. It sounds like an issue with your fuse links, which are the small loops of wire plugged into the harness near the positive battery terminal. Fuse links are basically slow-blow fuses, and shouldn't pop on their own--hopefully if they are bad, it's due to corrosion or mechanical damage. If a link is fried or broken, or its plug is corroded, or the guy didn't reconnect the fuse links properly when he replaced stuff (sounds like he replaced the terminal?), that'll be why it's missing power to places. Could be the guy screwed up; could be something was corroded and didn't give you trouble until he flexed the harness to get the terminal off the battery. But, yeah, check that your fuse links are intact, and if the terminal was replaced, make sure the fuse links are still connected to it. You may also have an in-line blade fuse holder hanging off the + terminal if your truck has/had the factory fog lights. This is unrelated. The wiring diagrams in the EL section of the manual may help you narrow down which fuse link(s) aren't working right if you can't find the problem visually. Not sure about the trans hesitation. Is the fluid level correct? Might not even be the trans. Mine had an engine stumble just off idle for a while, and IIRC it was that damn MAF plug.

Sounds like a trans cooler line failed, and the fluid level got so low in the pan that it was sloshing away from the pickup when you went around corners. Hopefully it's just the rubber hose that's failed. I didn't know Matic D was still available! I used generic parts store dex/merc when I flushed mine. Annoyingly I think I paid about the same amount for it.

EF&EC 155 in the '90 manual says 10-14 ohms. EF&EC 137 in the '95 agrees.

The computer just assumes you've got the distributor in the right place. It has no other reference to check it against. And, yeah, it has to be checked and set under the right conditions. I set mine cold once and it was way off once it warmed up. If you set it cold, with the timing light set wrong, who knows where it was set. I imagine increasing the advance would wake it up, to a point, until it starts pinging. No idea how far you can get away with on one of these. If it wasn't pinging, and didn't throw a knock sensor code, it probably didn't hurt anything. Might give you issues if you towed with it like that, though.

You could check it with a thread pitch gauge, measure the diameter, and see if you can find a nut of matching dimensions from McMaster-Carr or similar. Where I live, no way in hell I'd find a nut that size at Ace. If you have a larger hardware store with more than one short aisle of fasteners, you may get lucky.

GI-13 says the "connect" icon in your screenshot means you should test with the plug connected. Most connectors can be back-probed. You can get kits to do this more easily, but the way I do it (and I'm pretty sure there's a picture of this in the manual somewhere) is to wrap a thin wire around the lead on the meter, then stick the end of that wire into the back of the connector beside the wire that you want to test, so the test wire contacts the pin inside the connector. The box that says HS above the "connect" icon means the connector is shown from the harness side, which makes sense, as that's the side you're probing from. The wording is a little vague, and I haven't dug into this circuit on a round-dash truck, but I think they mean you should see 5v, then 0v, then 5v, then 0v, repeating as the truck moves. My understanding is that the speed sensor is a reed switch mounted next to a magnet on a shaft with a gear on the end, which generates a square wave signal as you drive. Each cycle (on/off) translates to a distance travelled. Try the test again, backprobing this time on the off chance that matters in this case, and see if that gets you a 5v square-wave signal. My '93 has the older style of cluster (square-dash), which has the speedo/odo driven by a spinning cable. The reed switch that makes the speed sensor signal for the computer(s) is built into the speedo. If you try the test again, and don't see the square-wave, I would check the harness between the speed sensor and the cluster, then see if I could test the sensor itself. If it is just a reed switch, you should be able to test continuity across it (harness unplugged, just the sensor), turn the sensor (could just put the rear axle on jack stands, trans in neutral, and turn the rear driveshaft by hand), and see if the switch cycles on and off as the shaft goes around. Again, I haven't tried it--but that's what I'd try next. Now that I think about it, I've got a round-dash speed sensor in a transfer case on my shop floor, and I'm pretty sure the speedo worked in the truck I pulled it out of. If I remember the next time I'm down there, I'll have a poke at that one to see if it tests the way I think it does.

I don't know crap about the R51, but I'll bet the service manual has trouble diagnosis info for the blower speed control, or at least a circuit diagram. Free download here if you haven't yet. Sounds like the hvac controls are stuck somehow. Could be the control panel itself, or whatever amplifier it talks to that moves the blend door and sets the fan speed, or the wiring between those things. Hopefully it's the cheaper/easier to get to one of those. Good luck!

No idea. Assuming the cluster stores the info on board, I imagine it would probably work. Check the '97 and '98 service manuals to see if the pinout is the same.

The e-fans are popular because they free up a little power at high revs. But, yeah, there's more to go wrong, and you may struggle to move the same CFM as the clutch fan when you really need it.

Wouldn't be a bad idea to check/replace the strut rod bushings, where the rear of the front control arms meet the frame. They're usually destroyed inside, even if they still look okay.

I remember someone (think it was my1path?) having some trouble adapting the VG30 TPS to the VG33 throttle body, which I assume wouldn't be necessary if the VG30 TB bolted up. Tuning may prove challenging. My1path got Nistune to work with his, Nefarious desoldered the eprom chip. Aftermarket EFI (megasquirt or similar) may be easier than working with what's there, especially if you're mixing and matching sensors as well. I remember someone on here had a hell of a time getting VG33 idle controls working with the WD21 computer, and that was without a supercharger (I don't remember why they didn't just use the VG30 intake). I've seen holes cut in the stock hood, so I'm guessing no, it won't clear. The Hardbody hood with the bump in the middle might clear. Write it up if you decide to try it!

I remember someone asking about it, but I don't remember anyone trying it. I doubt the bearings and gears would mind. No idea on the synchros. I know other boxes run ATF, including the T-5 in my dad's hot rod. If it was mine, and it worked alright, I'd stick with the standard oil. But it's not mine, and it has to come out anyway, so... send it and let us know how it goes.

Download the '94/'95 service manual for free here. EF&EC and EL will be your friends for this one, but you might as well download the whole thing. It comes in handy. Start with the check engine light. The EF&EC section will tell you how to get a code from the ECU, what it means, and what to check to chase it down. My money's on code 14, speed sensor. The transmission computer doesn't have a check light, but it'll flash the light in the E-AT switch after startup if it saw something in the last drive that it didn't like. The AT section has information for decoding those flashes. If you do see the flashes, I recommend recording them on your phone for easy playback, as it may take a few tries to read them properly. I haven't had to do one yet, but I've heard the speed sensors in these can be a pig to get out, and the drive gear may be difficult to track down/not included with the new sensor. Test and make sure you're on the right track before throwing a sensor at it. Good luck and let us know what you find!

I did this on mine. Haven't had a trouble code to run since I did it, but it's kinda fun to leave it in mode 1 and watch the oxygen sensor.

The MPFI intake uses a regular bolt as the bleeder. I've heard of the plastic bleeder on the TBI, but I don't think I've ever seen one, and I can't find a picture, let alone a listing. Does it look like a standard fastener, or does it have the center drilled out like a brake bleeder? If you can work out the thread pitch, you might find something close enough from mcmaster-carr.

Thanks for the show and tell! Always fun to see the inside of equipment I can't afford. I had wondered how the e-lockers worked. That ramp setup is actually very similar to the 4x4 engagement mechanism in a Ford transfer case I took apart a while back, except that one squeezed a clutch pack instead of pushing splines together.

The rear brakes may need adjustment.