Everything posted by Zed Head
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1977 280z prepup for smog check
So you're saying that he should trust what the FSM says and go ahead and short that switch? Assume that a direct short is fine and won't harm anything. Here's the post with the image showing the switch-like behavior.
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1977 280z prepup for smog check
I think that I would unplug it first and see what happens. That would be open circuit, super-high resistance, just like an ECU without an altitude switch. Then connect a potentiometer, set to open circuit/high resistance and carefully dial in some parallel resistance and see if you get a change. A new puzzle. Yay.
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1977 280z prepup for smog check
I would wait on that. If there's a spring and an adjustment screw it might not actually be an on-off switch. It might be a potentiometer that varies resistance by atmospheric pressure. If it doesn't go to zero résistance you might short something out in the ECU. It had been in the back of my mind that it would be odd to have a switch that made a dramatic on-off change at a certain altitude. Your observations kind of made things more clear. It makes more sense that it would be a variable pot. So, you might be able to put a potentiometer in its place. If somebody wants to study the AFM pin-out and see how resistance on that circuit affects the signal to the ECU, feel free. Pin 9 is one of the legs of the AFM potentiometer. My brain is starting to hurt...
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1977 280z prepup for smog check
I'd just unplug it and jump the plug. Like Dave said. If it works there will be 6% less fuel so the air-fuel ratio will be leaner. Should be enough to get you past the test. It might even run better and you can just leave the 40 psi FPR on and drive it that way. The ECU will just think you're in the mountains. But, if it were me, I'd try to understand the switch better first. Just to be sure that it doesn't have some internal resistance. Remove the switch and find a way to actuate it if you can. It's just an option. My car didn't have one otherwise I'd know more about it.
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1977 280z prepup for smog check
California was ahead of everybody else on emissions. If the thing has a port or opening on it you should be able to just suck on it and fool the ECU in to thinking you're at high altitude. You should hear a change in engine idle if it's running. Easy test.
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1977 280z prepup for smog check
The wiring diagram says it's in the cabin. Probably under the dash by the EFI relay. There's been a lot of talk about it but I've never seen anyone actually use it.
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1977 280z prepup for smog check
Here's the post that mentions it. You might have the switch that you can jump or might just have an ECU that will drop fuel by 6% if you short the pins. Keep it in mind.
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1977 280z prepup for smog check
I was reading Dave WM's Pikes Peak thread and realized that you might have an altitude switch. Keep it in mind if you can't get the FPR change to work, or try it before hand if you don't want to swap rails.
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Trouble Downshifting to First Gear?
It does say "or", for sure. The history of Dexron doesn't offer any clarity either. https://en.wikipedia.org/wiki/DEXRON I will probably just use Synchromesh synthetic fluid in any manual transmission I have in the future. Seems like some genius fluids engineer created the ultimate fluid and it works for everything.
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Trouble Downshifting to First Gear?
The ZXT 5 speed was made by Borg Warner. There is a bunch of discussion about the ATF spec around the interwebs. The ATF spec is correct, from what I've gathered. Some people suggest that the needle bearings might not get proper lubrication using the thicker fluid. I have a Ford 5 speed with Ford ATF, Mercon V, as the spec'ed fluid. It had shifting problems though so I switched to Pennzoil Synchromesh. Lower viscosity than 75W-90 but higher than ATF. It's been great and fixed the problem but the Ford guys say I'm going to ruin it if I don't use Ford product in it (that's what all Ford guys say though). That was 30,000 miles ago. Use this in the Google and there's a bunch - "borg warner t5 transmission fluid type".
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1977 280z prepup for smog check
No, more that you guys just have a better feel and familiarity with the equations. I had a vague feeling so plotted some numbers to be sure, but generally, practice makes better. Thought you guys might verify or have an opinion. Not one of my fortes. It was a good reason to rummage around the internet though. https://www.swtc.edu/Ag_Power/electrical/lecture/parallel_circuits.htm#:~:text=The sum of the currents,1%2FR3 %2B... https://www.swtc.edu/Ag_Power/electrical/lecture/series_circuits.htm https://www.swtc.edu/Ag_Power/electrical/lecture/ohms_law/ohms_law.htm https://www.swtc.edu/Ag_Power/electrical/lecture/combo_circuits.htm
- radiator
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1977 280z prepup for smog check
I think that using a parallel circuit flattens the curve, whereas a series circuit moves the whole curve up. The ECU expects a certain curve rate. Probably create new problems. CO and SteveJ probably draw charts in their heads on this kind of stuff. @Captain Obvious @SteveJ
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COVID-19
This seems to fit somehow...
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I want this lamp - cool furnishings
I got on the Google and found that you can buy them already made. Dang. More fun to make my own. https://www.carguygarage.com/accessories/decor/lighted-signs/billet-aluminum-distributor-lamp?gclid=Cj0KCQjw8fr7BRDSARIsAK0Qqr4x-kbhC6fU3Oxx0Ri-g0S_bB_WkhvBNxZwOSFqrWym0d6nBvDAOf4aAjAXEALw_wcB
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I want this lamp - cool furnishings
The lamp shade looks like an air filter! C'mon man!
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Trouble Downshifting to First Gear?
The fluid expands a lot though when it's warm. So, do it when the engine and transmission are cool.
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1977 280z prepup for smog check
Good point. I was thinking in terms of unmetered air not intake manifold vacuum. Another reason to just get an FPR that is in spec.
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COVID-19
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I want this lamp - cool furnishings
Watching the news about the crazy plot to kidnap the Governor of Michigan and noticed the lamp behind the guy talking. Check out the plugs in the base.
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Trouble Downshifting to First Gear?
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1977 280z prepup for smog check
He's in CA where they do the rolling 15 and 25 mph tests. The idle air bypass probably won't help much, I'd guess. He's so close, I'd bet that an FPR that has correct pressure would get him in spec. 40 psi is 10% high. Whenever I worked on my car to pass emissions (idle only) I would get CO and HC numbers that were much higher than he's getting and could get them to drop with small changes in fuel pressure (I had an adjustable FPR). He just needs a tiny change to get his CO numbers down I think. Tiny. Maybe, in the same vein as the idle air bypass, he could just open up one of the vacuum ports on the manifold. Maybe the one for the heater controls. The FPR is probably more effective though.
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Delphi Mechanical Fuel Pump stops pumping fuel
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Trouble Downshifting to First Gear?
Great news. Curious...was it low? Asking for future reference. Your problem doesn't really fit fluid change but might fit low level. Regardless, your transmission will be much happier with that fluid. On to the next problem. There are threads about the speedo connection O-rings. Can't find them right now but they do exist.
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Strut Cartridges Stuck (Rusted In?) Strut Housing
You could have drilled a hole in the bottom, filled it with propane and lit it, like a potato cannon. Wearing eye protection of course. 😵