Zed Head

Like I said, your idle sounded like 1200 - 1500 in the video. Sure didn't sound like 800. Doesn't matter I guess. If that's an old video, it might help to make a new "state-of-the problem" video. The point of the balance test isn't "all cylinders are firing" but "all cylinders are producing equal power". Or not. So you have to measure the rpm drop. For example, if you have a cylinder that drops spark every third firing, you might be able to measure its impact. I think that you might be at the point where you've done almost everything and decided that what you've looked at is all good. And you're looking for something that you haven't heard before. It's tough to help the guy that has done that and done that, etc. The miss from your exhaust sounded like a typical misfiring spark plug, for what that's worth. Have you done the "look for sparks in the dark" test? Here is one possibility for the low vacuum reading that might have merit - have you checked the PCV hose itself (the one underneath that connects to the valve) for holes or cracks or leaking junctions? I think that your pressure test of the intake system would miss that, because it would cause the valve to close, blocking off the crankcase. And the other parts of the system run through ported vacuum. Actually, I think that your pressure test only tested the manifold side and not the crankcase portion, so that might be worth double checking. The throttle valve closed off one end and the PCV valve the other. One other way to check for vacuum leaks (although without actually finding it) is to close the idle screw down all the way. The motor should die. If it doesn't, air is getting past the throttle body or leaking in from outside. I did that on my 78 motor and found that the Air Regulator was stuck open (probably not your problem, just an example).

The video and description help a lot. I don't have any ideas right now but did notice two things that seem unusual, compared to the two engines that I have played with the most, my 76 driver and a 78 parts car. The ticking noise seems much too loud to be injectors, it sounds more like a rocker arm or valve noise. My two engines are nowhere near that noisy, I've adjusted the valve lash on both. And your dwell/tach/volts meter showed 600 rpm, but I'm sure that your engine was up around 1200 to 1500 rpm (what did the dash tach show?). Maybe you had the setting on 4 cylinder instead of 6? The noise from the exhaust would be what I would call a "miss". Just for future reference. If you could drop the idle down (way down, to get a bigger effect), then pull the injector plugs off one by one (some people pull the plug wires but the stray sparks can be problematic), you might find the cylinder that is the source of your miss. The rpm should drop about the same amount for each cylinder that is working correctly. RPM won't drop as much for the weak cylinder. I think it is called a"power balance" test by some.

That's a lot of detail, except for the actual problem description. Is there any way you could get a video of the stumble? Does it fall flat when you hit the gas, or does it start coughing, or does it pop and buck, hesitate and go...? Does it do it with no load, or only in gear? 1st, 2nd, third or all? And "lower rpm" could mean 800 to 1000 or 1500 to 2000. Are you talking about just off idle or as you accelerate or cruising at low rpm? You didn't mention your timing either. Just trying to help, it's hard to tell what the problem is.

Here's a very late post to introduce the guy who walked in to the conversation and just started talking... I signed up for this forum over a year ago, just to look at the pictures. I didn't really expect to get involved beyond that but then I found a problem that seemed unique to my model year so thought I would share. Since then, I think that I've become hooked. This is great entertainment. I picked up a stock 1976 280Z in September 09, that did not run but apparently had at least idled about a year before I got it. Now, with information from this site and a few others, it runs and handles fine, doesn't leak (it's not a greenhouse inside), and I drive it almost every day. So far, no tickets or increased insurance rates. I have very low cash flow so I get a lot of parts at the local parts store and try to fix and improve existing parts before replacing. Hence the "Low Budget, High Value" under my screen name. It would be nice to get OE parts and see what the car was really like in 1976 but it's not an option right now. I'm kind of in between Hybridz and here, but with no welder, mill, bandsaw or metal brake. Just tying up loose ends. I know these sites take some work and can be aggravating at times, but I appreciate having them out here, and appreciate the guys with knowledge who keep coming back to share it.

I'm not sure what a "tcvas" is. If you mean TPS, then not hooked up is a bad thing. The TPS does not have any vacuum hoses connected to it. Blocking a vacuum hose hose won't do much. Pulling the hose will let extra air in to the manifold, which should raise idle speed if there is fuel available. On these EFI systems, all of the components are designed to work together. The ECU computer program takes input from all of them and adjusts fuel accordingly. There are only a few things that you can bypass or remove without messing things up. ... from my limited understanding in the short time I've worked on them.

A low idle seems odd. It should be easy to get more air in to the engine, raising the idle speed. What happens if you pull a vacuum line at idle? The idle speed should go up. At idle, the main one that goes to the carbon canister would be a good test. Even the little one that goes to the white vacuum jug should have an effect. Maybe your throttle position switch (TPS) contact is not registering "idle" to the ECU, so you're not getting idle speed fuel enrichment. This might give a low idle due to lack of fuel. The TPS is easy to check with an ohm-meter or test light. This is just a guess.

Read your post. Maybe too concise. Statements don't tell enough. Sounds like a vacuum leak or bad Air Regulator or both.

Z Tyler Z is trying to help you out. You're not reading his message right. I can see where you were coming from but also how things went wrong. That's text-based life on the internet. A poor communication tool - that's why they have emoticons and even those don't do much. Best let this thread die and start a new one if you're still looking for parts or advice. No response necessary or wanted. Pretend this never happened.

Do you have a new problem now? "Car driving and shifting fine" sounds like clutch is working fine. How does the noise while running and in neutral relate to the clutch? Maybe there's a word or two missing after "noise in" above...

It's about time! Timing is everything! Good times! How's the mileage? I advanced my timing a few degrees at a time until I was at 7 degrees over FSM recommended. The engine got more responsive each time. 2 degrees is pretty retarded. A doggy engine is a typical sign of retarded timing. Probably should have asked about it. Don't forget to followup, it's a good thread.

I sent it mainly for the pictures of the collars, so you could see what one was. Check out this link - http://www.oreillyauto.com/site/c/detail/WAG0/F131353.oap?year=1972&make=Nissan&model=240Z&vi=1209169&keyword=clutch+slave&forcedVehicle=true&pt=01352&ppt=C0015 What's interesting is they list the same slave cylinder for early 240Z's up to 280ZX's and including 240SX's. So I would guess it's not a big difference maker, or they are not different. Just another thing to consider. Also, the slave cylinders tend to go bad without obvious signs. Pull the boot off and see if any fluid comes out. It might be leaking mid-stroke, giving only partial movement. Which reminds me, the master cylinders do the same thing. But harder to tell. If you didn't have the odd drivetrain, all signs would point to a bad slave or master cylinder.

This web page has some good information - http://zparts.com/zptech/articles/trans_swap%20parts/4tobear_specs1.html If you're trying to match the bore of the master to the bore of the slave, have you considered a smaller bore slave? A lot easier if you can find one that fits, and the end result is the same. I don't know about specific interchangeability, but wouldn't be surprised if there was one out there.

Conedodger, this car uses the water temp sensor with the attached temperature vs resistance curve. I'm not sure what the CHTS sensor uses. But no continuity or high resistance would be "very cold" to the 77 ECU. Funky-P, from your answer, I'm guessing that you're looking at the wiring diagram also? Measuring 10 to 20 instead of 36 to 39. Still no numbers though, and no reports of fuel pump working (you can test it separately from the relays, just run 12 volts to it and listen) or fuel flowing. Don't forget that 0, 100, 180 and 1,000 ohm will all show "continuity." You really need the numbers. Read this thread from the past. Lots of good measurements and a positive outcome - http://www.classiczcars.com/forums/showthread.php?t=37299 . The major difference to your situation is that her car was running at the time. Still not clear why you're focused on the AFM. Confirm fuel flow, fuel pressure and spark first.

Use the "Edit" function and fix it...

You can do it either way. Still not clear on how you could be using page EF-52 but report "between 11 and 13 on any of the pins, 6, 9, 8, 7 in any combination." You didn't give any of your test values... 6 to 8, 9 to 8, 36 to 39. Sounds like you're checking things, but you're not telling the values you're getting. Or whether you have power to the fuel pump, spark, etc. Are you looking for the magic loose wire? Most people confirm fuel pump power, then fuel flow, check fuel pressure if you can, turn the engine over, check for spark, etc. Good luck, keep going, then come back later and re-read these ideas.

Well, thanks for following up on the response. I'm not sure which test procedure you're using though. The procedure I've used is on Page EF-52. You should get 180 ohms between 6 and 8, and 100 ohms between 9 and 8. Those are the two limits of the potentiometer and determine the feedback to the ECU from the flap position. If you're getting 11 - 13 ohms then you must be shorted somewhere. But then you shouldn't get proper readings from the flap. So we have conflicting results. Are you using a decent ohm-meter? 100 and 180 ohms are on the low side and may be out the range of your meter. Between pins 36 and 39 you should get continuity when the flap is open. That powers the relay that powers your fuel pump. Pins 6,7,8 and 9 should be tested to ground and should not show continuity. No shorts. Are you connecting 12 volts and measuring volts out for your flapper test? Have you confirmed that the fuel pump works and that you're getting spark? It's good that you're digging in but you might be jumping too far ahead. Edit - forgot to mention that you can take these measurements at the connector inside the car, with the AFM plugged in a grounded (or installed). The hardest part is figuring out the pin numbering at the connector but there's a picture in the manual, plus some of the pins are missing (not used). This way you test the harness and the component together.

He said he's a student so hopefully he's just young and ignorant, and doesn't realize the racist origins of his remark. It is sad though that I'm hoping for ignorance...

You might put your test numbers out here to be looked at. Some one could probably help you decide if they're terrible or not bad. Your car should start and idle with a bad AFM anyway, as long as the fuel pump contact is working. Your 77 still has the contact in the AFM if it is stock. I would get it started and idling first, then you'll have a better idea of how bad the AFM might be.

Fixing old posts - the relief valve in the stock Datsun fuel pump actually has a range of 43 to 64 psi. For future searchers...

Fixing old posts with new knowledge - The stock Datsun fuel pump reliefe valve (bypass above) had a range of 43 to 64 psi, not just 43.

Just fixing old posts with new knowledge. The JEGS liquid-filled gauge I discussed actually turned out to be very inaccurate once it got warm. It read low, disguising a high fuel pressure problem for quite a while. Stay away from liquid-filled gauges in hot environments, especially the inexpensive gauges.

You should download the Factory Service Manual (see the web site below) if you don't have one, get a multimeter and test things. The AFM test is pretty simple (it's in the Engine Fuel section). Some here have had good luck just cleaning the AFM contact area. I bought a remanufactured AFM but only after lots of testing to confirm it was bad (the resistance readings were off and it popped and bucked when I drove it). Spend a while testing components and you'll know what to think about when it still doesn't work right. Deoxit is a good contact cleaner but the others work well too. The electrical connections tend to corrode over time. http://www.xenons30.com/reference.html The 76 manual is broken in to chapters, the 77 wasn't last I looked.

Another Oregonian. Woohoo. How come you're not watching football? The thermotime switch only comes in to when play you're Starting. Maybe, instead, you jumped the temperature sensor that tells the ECU how warm the engine coolant is? If so, you told the ECU that your engine was very hot. Or you think you jumped it but actually just disconnected it. In that case, you told the ECU that your engine was very cold. That would give lots of rich black smoke. Did you just get the car? The symptoms look like those of a bad AFM. I had a bad one and mine idled fine, went well at 3/4 to full throttle, but did what you describe at part-throttle. There is a test procedure for the AFM and most of the other EFI parts. You can spend a lot of money replacing parts, when all you might need is some contact cleaner. By the way, your first post was pretty well formatted except for the large, bold font. Second one looked like cell phone.

I was in the FSM the other day for some reason, and realized that on Page EF-15, the description of the relief valve says "43 to 64 psi". I too was under the impression that the relief valve let go at 43 psi and have stated that several times myself in previous posts. I'm not sure how I missed the 64 psi upper limit but it should be noted that 64 psi is a possibility. So it is possible to have a plugged line or regulator and get pressures considerably higher than 36 psi. It would be interesting to pinch off the return line completely on a stock fuel pump and see where the relief valve lets go. Might not be safe though.

Thanks for reminding me. I do remember reading some posts about that, with descriptions of the bearings that would work. I'll search it out.