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Distributor questions- 280zx Turbo


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I have it timed! It idles much better now. It also doesn't have an oxygen sensor. The sensor body broke off, and the bolt head is rounding off. I'm going to try to weld a nut to the top of the remains of the sensor, but I strongly suspect the lack of the oxygen sensor is the cause of the last issue I have, which is a general coughing and backfiring when under load while I'm not in boost. Once the engine starts making boost, it's fine, and has loads of power.


Other than that, I think I can say I've successfully rescued this Z from a kid who had delusions of a drift missile Z.

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Well, it's done. Vacuum lines replaced, plugs and wires replaced, the engine timed, O2 sensor and cylinder head temp sensor replaced. Now it runs smoothly, and has plenty of power! And now I have more movies!  I'd like to thank everyone who replied in this thread and helped me get the car running over the last 5 months or so!


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So after a long drive, a couple of hours, I found new and interesting problems. Car doesn't quite idle smoothly, and sometimes under power, it'll start to run rough, and backfire a few times, before it smooths back out. As near as I can tell, I'll probably want to replace the tired old fuel pump (It's a factory original unit) and get my injectors flow tested; 34 years and it's been sitting a lot of them, I'm sure I have fuel delivery issues. I also think I still have a vacuum leak, which I may have isolated; The rubber boot that comes from the back of the AFM, to the turbo intake. Other sources have mentioned it can get hairline cracks from years of the small flexes it has, and can be a source of unmetered air. So I did some shopping, and nobody makes an aftermarket one, near as I can tell. All that's out there is used, or NOS. No problem though, a silicone tube as found on every turbo car ever would do, except one engineering problem I can't suss out.


The valve cover breather tube. It vents via a hose to the post afm intake boot. Stock car has a rubber nipple that a steel coupling pipe goes into. But I can't figure out now to do something similar with a silicone boot, and make it airtight. But I bet someone else has done that, because I can't be the only stock ZXT left in the world. Anyone found a solution to this? Or has the go-to solution been to put something like a PCV check valve in the breather and put a filter on the end of that? That seems to me like a vacuum leak waiting to happen, but I wanted to put a feeler out and see if anyone else had tried this sort of thing.

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Exhaust backfire???? This is usually caused by a plug or two not firing and the air an fuel mix exploding in the tail pipe. I'd look at the distributor and coil wires, the rotor and the cap. If old, they may allow the spark to jump around. Check also the coil high tension tower. If cracked the spark can jump to the negative terminal. Spark always looks for the easiest path to ground.... make the easiest path the spark plug and you're good.


Another source of poor running under load is tight valves. Get the valve lash checked.

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Oh. I hadn't even considered the coil might be the issue. I'm a dum. I'd been so focused on vacuum and fuel delivery. Plugs and wires are both new, so should be okay. I'll see to inspecting the coil and maybe dropping on a replacement unit. I've got some spare parts from my old '80 ZX and a coil is among them, never been out of the box. I might toss it on and see if anything improves.


As far as valve lash, the 83 FSM has all valve adjustment procedures listed as "Model without turbocharger". I presume that's because my head, a P90A, has hydraulic lifters. And yes, I do know it's a P90A as that's the casting number on the side of the head. I have no reason to suspect that it's been modified with solid lifters, given how stock everything else is.


I know from my days with aircooled VW, VW liked to say the hydraulic lifters never needed adjustment, but they could be adjusted, and there were unpublished specs. Are the Nissan hydro lifters truly maintenance free,or is there actually a ash adjustment that can be done on them which is not documented in the fsm?

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