Slartibartfast

I ran mode 2 on mine today. Same as yours, both lights flash. So the computer thinks the mixture is okay, for whatever that's worth. And yeah, OBD1 is a pain.

EF&EC 26 of the '95 FSM says that in mode 2, at 2k rpm, no load, warm engine, the red and green lights should flash, together, more than five times in ten seconds. I don't know why they didn't list that spec in the description for the test modes. I don't know what to make of your twenty seconds on/four seconds off. Trying and failing to enter closed loop? Are you checking at idle or at the 2k rpm spec'd? They don't stay in closed loop at idle, or at least mine doesn't. But I wouldn't expect that result at idle, either. I've got some driving to do tomorrow anyway. I'll set it to mode 2 after and see what derblinkenlightzen have to say. I'm reminded of the usual failure symptoms of the distributors in these. Runs fine when it's cold, starts running like crap as it warms up. Ignition misfires could explain both the high hydrocarbon readings and the rough running. But from what I've read, those tend more towards stalling out and not running at all. Could be that the cold high idle is just masking whatever is wrong with yours, and that's why it gets worse as it warms up.

The '03 service manual says the cam sensor code (P0340, P0345) is set if the computer doesn't see a cylinder number signal in the first few seconds of cranking (could be due to a low battery or weak starter not turning it over fast enough), or during engine running, or if the pattern of that signal is "not in the normal pattern." It suggests checking the sensors, connectors, battery, starter, and the intake camshaft. The manual has some troubleshooting instructions that might be worth going through to rule out the wiring. (The manual is a free download from Nicoclub, and you want the EC section, page 357.) Could be a harness got pinched or a connector broke during the head gasket job. Outside of the manual--assuming all that stuff tests normal--I suspect your timing chain is off by one tooth on the bank that's coding. I suspect this because my dad's Tundra threw a cam sensor code when its timing belt slipped. The sensor was fine, but I guess the timing being a tooth off put the sensor's signal outside of what the computer considered normal, and it wasn't programmed to check for cam/crank correlation, so it blamed the sensor. I don't see a correlation code in the '03 R50 manual, either. And we know someone's been into your timing recently, because a head was off, which was when the issue began. (That's a long way of saying +1 to Adam's thought that the mechanic put it back together wrong.) It's weird that it's taking an hour for the code to appear. I've heard of codes only tripping after a fault is detected however many times. Maybe it just takes an hour for the computer to admit that it has a problem? I would check for pending codes (assuming your scanner can do that--my cheap one can) and see if the code pops as pending soon after startup. And yeah, the VG is a gutless wonder, but I do not envy the complexity of more modern engines.

Hopefully yours don't look like that! A couple did in the VG33 I was going to put in mine, and some of the missing material had found its way past the pickup screen and chewed up the oil pump. The crank and cam bearings were all shot, I assume from low oil pressure. It still ran surprisingly well.

I had a whistle from the intake tube on mine a while back. Drove me nuts. Near as I could tell, it was the sharp edge on the bung that the pipe feeding the idle air control goes into. I "reshaped" it a little with a big drill bit and it's been quiet since. Engine ran the same whether it was whistling or not, though.

Maybe dripping fuel from an injector, or leakage from the pressure regulator into the intake? I'm still trying to think of what would make it oscillate. Also thinking about it again, I would expect a vac leak to cause NOx issues, not HC.

The transfer case takes ATF (Dex-Merc), and the manual transmission takes GL-4 75W90. Make sure it's GL-4! GL-5 rated oil (which is much more common) will eat the synchros. The drain plugs should be pretty obvious once you're under the truck.

Bouncing back and forth sounds more like an EFI issue than a cat issue to me. Lean condition--check the vacuum lines, the intake tube between the MAF and the throttle body, and the MAF itself. If the MAF is covered in schmutz, it'll read less air than is actually going past it.

I'm running a Magnefine on mine as well. I don't know that it's strictly necessary, but I wanted to give my high-mileage slushbox every chance I could, especially after seeing a little glitter in the fluid when I flushed it. I routed the lines on mine so the fluid goes from the trans, through the stock cooler in the rad, through the aux cooler, through the filter, then back to the trans. My thinking was that the OE cooler can only bring the fluid temp down to the coolant temp, so it should be the first stage. I put the filter on the return side just in case the cooler (which was not new when I installed it) had some schmutz in it. That I don't know. But I've had the filter on mine for the last 30k miles, and it hasn't complained.

So it's going back and forth between good and high? The mixture's actually supposed to bounce back and forth a little when it's in closed loop, that's how it controls the mixture with a narrowband oxygen sensor. Maybe the sensor's on its way out and it's responding very slowly? There is a test mode for the oxygen sensor, might be worth running that to see if the light's flashing like it should. Some codes don't trip the light, so I'd run those too on the off chance.

The torque spec for the bearing lock nut is 4.3-13 inch pounds--just enough preload to get the play out of it, plus what it takes to get the screws in. Sounds like you ran yours at roughly 70x their intended torque. I've never run a bearing that tight, but yeah, I'd lay money that's your problem. I don't think I'd trust that set of wheel bearings to go again.

That's a weird one. Wonder if someone popped a fuse somewhere else and "borrowed" it? Glad to hear it was a cheap/easy fix!

My (limited) understanding of the SFD is that it's basically the unibody equivalent of a body lift. Suspension lifts mess with the front end geometry, and cause more problems the higher you go. IIRC the R50 gets unhappy if you go past about 2" of suspension lift. A body lift or SFD leaves the geometry alone and just shims the body up over the existing suspension. So apart from the higher center of gravity (which you'll get from any lift), I wouldn't expect the SFD to make much difference to the handling and alignment--or at least it'll work better than it would if you tried to lift it the same amount by modifying the suspension.

I had a look at the circuit diagram on EL-251, here. If we assume that the two faults have a common cause (not guaranteed, but does seem likely), then it's gotta be between the battery and the cruise switch on the steering wheel, because that's the only section where the cruise and horn circuits overlap. The clockspring has a wire in it that's shared between everything that's not working (horn and all cruise buttons except "main," which I assume is the one that works). Naturally you've already replaced that. The coil in the relay could also break both circuits if it was bad, but you've replaced that too. That leaves the switches/wiring inside the steering wheel, or the wiring between the battery and the wheel. I would start by testing fuse #52, 7.5A, which runs one of the horns (for some reason the two horns are fused separately), the horn relay (which means this one fuse will still take out both horns if it's bad), and also those three cruise buttons. Check with a test light (with the other end grounded) that you have power at both legs of the fuse. One leg means it's dead, neither means there's an issue between the fuse and the battery, both means it's OK. If there's power at the fuse, then it's a question of what you want to tear apart first. I'd be tempted to tear the wheel apart first and test that it's getting power at pin 1 (pin 12 of the clockspring), as labelled on EL-253. (I'd test this with a meter, because the resistance of the relay coil might be too much to work an incandescent test light.) If it's got power, I'd test the switch next. If it doesn't, then there's a break between the fuse and the switch. In that case I'd check the other side of the clockspring (to verify the clockspring's good), the connector on the light green/black wire shown on EL-253 (no idea if that connector is just that one wire, or a bunch of them, but it would be a convenient test point if you can find it--or a possible source of the problem if it's loose/damaged), and the horn relay connector. Once you know which two points you lose power between, you know what part of the harness to investigate. Hopefully it's not the harness. That's all I've got. Good luck with it and let us know when you figure it out!

Yeah, it's not a big engine. I took apart a VG33 a while ago and was able to carry the block around pretty easily, and I'm not exactly corn-fed. I saw a guy on Youtube put an LS in a D21, and he ended up notching the crap out of the firewall to get it in there. Ecoburst could be entertaining, and Nissan got a four-pot in there, so surely there's room. Speaking of, there's also a kit to bolt a VW diesel to a Nissan gearbox.