Zed Head

I put a single relay on my 76 to take the heat out of the switch. If I recall right you just cut the red wire from the switch to the fuse panel and insert the relay there. I punched a hole through the rubber plug in the firewall to the battery terminal. Full power still runs through the dimmer switch but the combo switch only sees the amps to actuate the relay. The circuit is kind of odd to look at because power comes through the switch from the W/R wire (on a fusible link circuit) then passes through the switch on the way to the fuse box. So the relay doesn't control power in to the switch it controls current out. Instead of supplying the fuse box through the switch you supply it through the relay, controlling it with the red wire out of the switch. I have vague memories of posting (maybe just thinking) incorrect logic about the fuses in the past, I think because my thinking was backward about the current direction. (One way in which the internet sucks. The internet forgets nothing.). I thought that the fuses saw less current with the relay in place. But they see the same current just from a different source, the power still passes through the fuses on the way to the headlights. Assuming my 2022 logic is better than that past logic. I could be wrong. Only adding in case someone sees an old post. Maybe I'll dig it up myself. (Just remembered that the fusible link is actually taken out of the circuit, not the fuses. Rambling...) p.s. if you take a few minutes and study that headlight circuit you see that there is "potential" in the factory setup to run 40 amps (assuming a green fusible link is 40 amps) through that tiny switch if there's a short in the red wire that heads to the fuse box. Seems like the switch might melt before the fusible link. p.s. 2 - the running lights run through the circuit right next to the headlights. It's just a bad design. Lots of heat.

So you destroyed two other BCDD's/TB's? Not good. Anyway, at least one problem down. Good luck.

Multi-quote doesn't work across two pages weird. Had to stick an image in there instead. You had a block-off plate on the other two TB's? Just wondering....

I think that he has a Hall sensor on a modified Jeep CAS. And he has coil on plugs, AKA COP, controlled through the Haltech system. Could be a coil circuit in the Haltech ECU, or the tach circuit with all six coils ganged, or maybe the Hall sensor on the CAS. Lots of things to check. Meter time. Check, check, check , check...

I don't want to muddy up the waters either. But a "full" short would completely fry the insulation and the wire very quickly. That wire has just seen too much current for too long. But there is a load, some resistance, between the source and the ground somewhere. Have you measured resistance through that IAC valve? Easy to do and worth verifying.

Found a few. https://www.classiczcars.com/search/?q=bcdd block plate&quick=1

It's probably the solenoid valve for the vacuum advance supply hose to the distributor. For some reason Nissan only wanted the early years to have vacuum advance in 4th gear. There's a switch on the transmission.

Pretty sure that CO has posted that you can't just put a plate on the BCDD mounting area. There are passages that will still be open, that you have to block. Pretty, pretty, pretty,sure. But not positive. Search around on Captain Obvious and BCDD.

The BCDD is a known idle speed screwer-upper. It's on the bottom of the throttle body. It lets air past the throttle blade under certain conditions. You might try one of the other TB's.

p.s. what's up with your oil pressure gauge? Disconnected at the engine?

I think that the shim is meant to correct for the expansion of the aluminum case when it heats up. And/or it locks the outer race down so it won't spin. It's basically a preload shim. Too loose and the race might spin. That's my guess. I also remember finding that all of the ones I measured were 0.3 mm. Like Nissan figured out their manufacturing problems and they were all identical. The picture seems to show that it rides on both races but I thought it only contacted the outer. Could be wrong, can't remember.

I'm going to guess that the water pump is not pumping or is pumping at a low rate. Maybe there's a blockage. The hot coolant is just moving slowly by the sender right after it picks up the extra heat from the "load test". In the garage with no load, the extra RPM move the coolant just a little bit faster pulling cooled coolant through from the radiator. The gauge needle behavior looked normal, plus it started from the correct spot for an idling warmed up engine. The proposal of a bad sender really just means that it's correct at about 180, but shoots up ~10 degrees / real degree after 180. It might be scary to do but if you load tested at higher RPM you might get a different result. Keep the revs up to keep the coolant moving. Just trying to fit the puzzle pieces together. When you dump the flushing chemicals you might remove the top radiator hose and see what kind of flow you have. Don't drain it, use the engine and water pump to push it out. Another data point...

This is the most likely cause of the noise. The system is not "intact". During normal operation of an engine with normal blowby there won't be very much flow through the valve. Just enough to clear out the gases.

You got my point backward. The "CAI" lets the noise out. The factory air filter keeps the noise in. It's just normal air flow noise.

Put the factory air cleaner back on and see if it's still there. Automotive engineers spend a lot of time figuring out how to quiet intake noise. People pay good money for "cold air intakes" to get that noise.

He said they took it off.

I noticed that too. Plus they edited in footage from behind the car but didn't change the soundtrack. The guy said that he took four trips down the mountain to get the footage. Pretty sure I heard a gear grind in the video also. I think that they just over-produced on the video. It's in the "collector" zone, early car, very original, etc. Collectors don't want to see people beating on their dream car.

I watched the video and don't hear the noise. Are all of the various vacuum ports on the intake manifold used or sealed? Charcoal canister, AC system control, brake booster, etc.

That's what I meant. You didn't answer so I couldn't tell. With no throttle body there is effectively no vacuum being pulled on the intake manifold. So any leaks that would make noise with vacuum will stop making noise. Could be an injector seal, the gasket around the cold start valve, intake manifold gasket.

If the system is not intact you can suck a lot of air through the PCV valve. How did you keep the engine from revving to 8000 RPM with no throttle blade?

So you can sit in the garage and let it rev at 3000 and no heat increase? Just trying to add something. The more words the better. Good luck.

That was after the driving. I'm wondering about repeatability under no-load conditions. Just another clue. You don't have many right now.

Is the PCV system intact? Might be pulling through the PCV valve on the bottom of the intake manifold.

If it moves up and down with engine RPM then it must be sensing the current. Since it's designed for a 4 cylinder engine you'd think it would be more responsive on a 6 cylinder, not less. 50% more sparks than expected. Kind of sounds like it has problems.