FastWoman

Argneist, I edited my post (#4) while you were in the process of typing a reply to it. I can see that you used the "T," thereby blowing that theory of mine. It sounds like you hooked it up correctly. And no, you wouldn't want to hook it up anywhere else. If you already have the fancy job, there's no point in cobbling together a lesser gauge. You can probably check your gauge against another accurate gauge, using compressed air. It's hard to say what's inaccurate. Gauges are generally pretty accurate, and so are FPRs. I would think that an FPR would regulate lower with age, if anything, due to weakening and rusting of the internal spring. Dunno.

Might be a bad FPR. Like Steve, I just made my fuel pressure gauge from hardware store parts. I think it cost me about $15. It's surprisingly versatile and accurate for something made in China. It probably reads within a psi of being correct, in comparison with some better gauges of mine. I agree with Steve about gauge installation. You only use the thing for diagnosis, and pulling hoses isn't a problem in that case. A permanently installed gauge is just one more thing to go wrong. The only point in its favor might be that it looks cool, which is certainly a valid reason, if that's what you're after.

So to be clear, you replaced the thermostat, and the engine STILL won't heat up to 180? And when you drive it, vs. idling it, the temp will STILL fall? Maybe you got a defective thermostat. (It wouldn't be the first time this has happened.) What you describe are classic symptoms of a thermostat stuck open. With regard to heater core issues: Your '77 and my '78 are very similar designs. My '78 has two stopcocks on the heater core. One is vacuum-controlled and turns the coolant flow on and off, depending on the mode switch setting. The second opens and closes variably and is controlled by a wire from the temp lever. You should check to see that both function correctly. (You can reach up and feel these stopcocks with your hand, and you can feel them operate when you turn the levers.) In my '78, the mode selector switch was gummed and crudded up and didn't hold a vacuum. You can take it apart and lubricate it with dielectric grease to get it operating again. It's a simple part, and nothing will explode. However, you have to be certain to correctly align the gear teeth when you R&R. You can read about it here: http://www.classiczcars.com/forums/showthread.php?t=35521 Also make certain you have vacuum to the selector switch, It's very easy for someone to pull the little vacuum line off it. Leaks and breaks are also commonplace.

Jenny, your air regulator wouldn't affect your mix. The air it lets through (to raise your idle) is metered, so it will come with extra fuel. FAIW, my air regulator gives me about a 1k idle cold -- lower than the normal high idle. Maybe it's a bit sluggish or defective, or perhaps it needs adjustment. Anyway, I don't consider it an important issue, because my car idles just fine at 1k when it's cold. I'm sure without the air bypass, the engine would barely idle at all when extremely cold, so the air regulator is clearly doing something (and doing it well enough). As Eric said, the coolant temp sensor with the 2-conductor Bosch style connector is the one for the EFI. The one for your gauge has the single wire. There's another doodad in the thermostat housing with a two-conductor Bosch-style connector, and that's the thermotime switch. You don't want to mix the temp sensor and the thermotime up! I'm almost positive the thermotime has the larger base to it. You can verify either by checking for zero-ish ohm continuity between one of the pins of the temp sensor connector and the #13 pin on the ECU connector -- or -- by verifying zero-ish ohm connectivity between the thermotime connector pins and the cold start valve pins. Anyway, do your temp sensor resistance measurements at the ECU connector for the most meaningful results. Wait until your engine is stone cold and at a known temperature, so that you can compare to the correct value ranges in the FSM.

When I was a kid and owned a '75, I oggled the headlight covers. I thought about getting a pair but never did. Now with my '78, I became aware of the G-nose option that I think looks incredibly sexy. However, my '78 will stay stock -- no G-nose and no covers. I love the stock look of the 280. It's its own automobile and doesn't need to look like any other. Moreover, it was emblematic of a generation of import sports cars back during "my" day. I admit it will be with some reluctance that I may do one small mod on the rear bumper, to bring it in just a bit and to modify the bumper covers to eliminate their odd protrusions. Some people hate 280 bumpers, but I think Datsun did a wonderful job working with the difficult requirements imposed on them by the US market. Their floating front bumpers are unique and, I think, cool! Yeah, I like the 280Z for exactly what it is. But yes, like you, I'm in love with the long hood, long engine, and slung-back cabin.

Buddy, I see you have a '77 -- EFI. I had an intermittent problem with my '78's fuel pump wiring. Maybe yours is the same. There are a couple of large wiring harness connectors just on the cabin side of the passenger-side firewall. They might be covered by a piece of trim plastic. The fuel pump wire runs through the corner of one of those connectors. I believe it's blue with a green trace, but I'm not certain. Anyway, that connector carries a lot of current and can cause arcing and melting in the connector. I tried cleaning up mine a couple of times, but the connection continued to be problematic. I ultimately snipped the wire out of the connector and connected it via a bullet connector. I haven't had problems since. Other than that, just start looking for charred connectors. You'll likely find one.

Hey Jenny, great news! What would cause you to run rich? Dunno... Is your coolant temp sensor reading correctly? That's probably the biggest thing affecting the mix. If it's reading too high a resistance for a given temp, you'd be running rich. Same for the air temp sensor, except that would have a lesser effect. If I remember correctly, I had a rich running condition in my '75 280. It was caused by a bend in the AFM vane assembly from engine backfire. I fixed the problem by tapping out the vane with a hammer. The '75 AFM vanes didn't have backfire relief valves. I think they fixed that in '76. I doubt your ECU has drifted to the rich side. Most linear circuits tend to break down in a similar manner across units. Anyway, if you're running correctly on the road and are idling incorrectly, you can tweak the idle mixture by turning the idle mixture screw near the outlet of the AFM towards the bottom. You'd screw it in to richen the mix and screw it out to lean it. (This adjustment affects only the mix at idle.) That said, I didn't find the screw did much on my car. I set it at 5 full turns opened up from fully closed (fully clockwise), but this was arbitrary.

Ah, but you used duct tape, Eric! Not nearly so elegant as Yoplait!

Then it's not just on startup??? I'm confused. I thought from post #8 that I understood what he was referring to. I would think that any issue that both comes and goes while you're just standing there looking at the car idle almost HAS to be an intermittent electrical problem. Are all the electrical connections clean? Are the connectors in good shape?

Sounds like y'all should embrace the continuation years!

I keep telling people about my yogurt cup test, but nobody else has tried it. It's low-tech, but it works brilliantly: 1) Go to the grocery store, and buy a 50 cent cup of yogurt. 2) Go home and enjoy the yogurt, as you ponder the task ahead. 3) Rinse and dry the cup. 4) Remove the AFM. 5) Stuff the yogurt cup into the AFM-to-throttle boot, thus sealing it. 6) Pull off the brake booster vacuum hose, and put another clean hose on it. 7) Put the other end of the hose in your mouth, and blow, so as to pressurize the intake. Then hold the pressure with your mouth. The pressure will slowly leak down. Note roughly how long it takes. 8) As a frame of reference, pull a small vacuum line off, and repeat the test. Air should escape remarkably faster with the small vacuum leak. If this difference is remarkable, then the sum of your leaks (including valves, rings, etc.) shouldn't be any larger than that one small vacuum leak you created, which wouldn't be particularly significant by itself. Cheap Fast Easy Conclusive -- allowing you to answer the "do I have a vacuum leak" question and move on. Please PayPal me all the money this method would have saved you.

Bavarian, I'd just pick up a basic how-to book, in addition to the factory service manual for your car (about $80 off of Amazon or Ebay -- used, of course). With basic tools, plus a set of feeler gauges for spark plugs and point gaps, plus a good timing light, dwell/tach meter, vacuum gauge, you should be able to do all your own basic work. Like anything it's a learning curve, but you'll have fun doing it. I disagree with the "if it ain't broke" advice. Many parts go bad gradually -- e.g. plugs, wires, cap, rotor, points -- so there's no obvious point at which they're "broke." The engine will simply continue to lose efficiency, as you shell out too much $$$ for expensive gas. I think most people drive their cars until they won't "go" anymore. Then they wonder what's wrong, and they expect it to be a single thing. Often a mechanic will fix a single thing, maybe two, and get the car to run again, albeit not well (since there are other problems remaining). However, the truth is that a car your age generally has MANY things wrong with it, even though it "runs good" (which is one of my favorite phrases from car ads). You should never let problems accumulate. People who stick to recommended maintenance schedules generally have better-running cars. People who drive until the car won't go anymore generally do not.

Jan, I had your exact restart / rough idle issue. One way or another, the problem is air inside your fuel rail. When you try to start the car, you're injecting air. Once the fuel pump is able to purge the air through the return fuel line, approximately half of your injectors are still going to be injecting air, because the fuel rail is in a loop, and only one end of the loop will initially get purged (whichever one is lower). It will take longer to work through the air in the higher end of the fuel rail. So when you eventually start, you're running approximately on 3 cylinders, although conveniently you're missing every other explosion in the firing order. Then your other three cylinders will catch, one by one, as the air is purged. Probably your #1 or #6 will be the last to catch. Solutions: 1) Get your fuel rail tight. You've replaced the injectors, aside from the CSI. My CSI was frozen partially open, and I replaced it with a used part I had on hand. I then got my original one cleaned out by flushing with Chemtool B12. It holds pressure now. Finally, there's the fuel pump check valve, which Cozye correctly indicated is NLA. Even the corresponding Volvo check valve seems to be NLA. I know, because I probably bought the last one in the country. Another solution that might work is an inline check valve, which you could place inline between your fuel filter and fuel rail: http://cgi.ebay.com/ebaymotors/One-way-Check-valve-Gas-Diesel-fuel-5-16-Bio-_W0QQcmdZViewItemQQhashZitem230dbe3583QQitemZ150554424707QQptZMotorsQ5fCarQ5fTruckQ5fPartsQ5fAccessories I had checked with the seller to determine that it would work fine for 30'ish psi pressures. He said it would be. I don't know anyone who's installed one, but you could be the first to try it! 2) If you can't get your system 100% tight, and/or if fuel vaporization becomes a particularly difficult problem down there in AZ, you can install a primer switch that will manually power the coil on your fuel pump relay. I did this on my '78, prior to working through the leaky fuel rail issues, and it worked magnificently. With the primer switch, you can just run the pump until the air is purged. About 10-15 sec of purge will even clear the bubble in the higher end of the fuel rail, assuming you're on a reasonably flat surface, so that your engine isn't coughing and struggling when you turn the key.

Hey Jenny, I'm back. Sorry for my long absences. We're randomly leaving town on real estate matters (looking). It's not a permanent sort of thing -- or BETTER NOT BE! This will all get a bit better for me when the roads are cleaner, and I can drive my Z. (Well, or we can take the little Miata. Either is a pleasure to drive, but I do prefer my Z.) The EFI is somewhat of a black box system, so it's hard to know EXACTLY what info the ECU uses from the AFM. However, if I were designing the system, using a potentiometer (e.g. the AFM) for input, I'd send a fixed voltage through both legs of the potentiometer and tap the voltage off of the wiper, sending it to a high-impedance input circuit. The objective would be to avoid passing any sort of real current through the delicate wiper contact. That would minimize oxidation of the contact and would maintain accuracy despite wear. If I could have input into the potentiometer design, I would also have a high precision resistance ladder alongside the main carbon trace to stabilize the relative voltages. Anyway, the AFM seems to be constructed with all these design attributes, and I suspect the ECU does pull off the voltage from the wiper (not a current) via a high impedance circuit. It would only make sense. With this sort of design, absolute resistance values aren't nearly so important as relative resistances. (It's a design that can age rather gracefully.) The most important thing is that the carbon trace and the wiper contact are both clean and protected from oxidation (via a thin lubricant film). Anyway, could your AFM still be out of spec? Well, maybe. Maybe mine is too, although I certainly verified all the resistance readings and made certain I had a smooth voltage gradation from full-closed to full-open. (Note here: You have to use a needle-movement multimeter to pick up on any jitteriness in the voltage output -- preferably one that isn't nicely damped. Oddly, a cheaper meter is going to do a better job.) That said, even if your AFM is out of spec, you could still tune your system reasonably well with that potentiometer in series with the temp sensor, assuming the error is to the lean side (but possibly even to the rich side, using a method I haven't had occasion to try). Would it be perfect? Well, maybe not PERFECT, but it would still be close, and it would be a whole lot cheaper than a rebuilt AFM. In fact a manually tuned system with a slightly-out-of-spec AFM is probably going to deliver a better mix than an untuned system with a rebuilt AFM. FAIW, I also have to wonder what these rebuilding companies do when they rebuild an AFM. Do they replace the potentiometer assembly? Or do they simply clean the unit up, verify proper functioning, make it look pretty, put it in a nice box, and ship it out? I strongly suspect it's the latter. I also see items such as rebuilt ignition modules and ECUs, and in that case I know it can only be the latter. In fact I suspect some rebuilds even skip the step of verifying proper functioning and simply hope that the part won't come back. I could be wrong about this, but I'd be surprised. Oh, you asked whether the AFM could suddenly develop bad resistance values. IMO, the answer would be "no," unless one of the resistors went bad and opened up (not likely, especially since you're getting close to the right numbers). OTOH, I would think a new vacuum leak could be a sudden thing. You found a few of those along the way.

FAIW, Eric, I had some trouble adjusting my idle down all the way too, once I corrected a few problems with my intake. I actually had to adjust the throttle stop screw just a bit to give myself the needed adjustment range with the idle screw. It was VERY small adjustment! Jenny, I'm sure the valves are good at 15k miles. That said, the guy who last adjusted my valves before I bought my Z was a certified Nissan mechanic, and two of the valves were TIGHT, almost to the extent of not allowing complete valve closure. That tells me they weren't properly adjusted in the first place. Just saying! You may think your problems are more ignition than mix, and they might be; however, a bad mixture problem can feel like an ignition problem, and vice versa. I really beat my head against a wall chasing down ignition problems that maybe didn't exist, before I finally corrected the mixture problem. Our new car -- It's not registered yet! We're trying to locate some other paperwork we need to take in to the DMV, so as to kill two birds with the same stone. So the little Miata has been sitting there in the garage. It's not been a good time to drive, though, so it's just as well. Besides, we're busy with real estate stuff. No time for having fun.

Wow, I've only been away from my computer for a day (increasingly dealing with real estate issues), and you're bubbling over with frustration! I have to agree, though, that your car needs to stretch its legs a bit. That will improve the condition/running of the engine, and perhaps more importantly, that will give its mechanic the emotional re-charge she needs to continue forward! I don't know whether to nod in agreement with Eric about your not having a lean-running condition. It's true that you're exhaust is popping. However, you might get exhaust popping if you have a bad misfiring situation and are blowing raw gas and excess air through the exhaust from a non-working cylinder. I once blew out one of the cats on an Expedition that way. Otherwise the mixture was spot-on. You might also be getting carbon on your plugs from partial burns. My plugs looked a lot like yours even when I was running extraordinarily lean. So I wouldn't close the book on a possible lean issue YET. I do think the best way to determine the ideal fuel mix is to tweak the AFM vane with your finger and see which direction of tweak, if any, makes the engine run faster and with more vacuum. It's true that that tells you more about idle than running under load, but it's quite difficult to take measurements under load, unless you're on a dyno. Still, this approach got me quite close on my car. FAIW, my idle mix screw was/is adjusted 5 full turns open from full-closed. Anyway, this approach will tell you the proper mix irrespective of engine misfiring. So your afterfiring could be caused by a rich mix, but it could also be caused by an ignition failure. If I were you, I'd get all the ignition issues squared away first, and then worry about the mix. That includes the distributor, and proper timing, of course. I'd table replacing the coil or ignition module for now. I replaced both and saw some (but limited) improvement, but in truth, the problem was an extremely lean mix, and if I had straightened out the mix, the coil and IM might have been good enough. After you get the distributor squared away, let's re-tweak the AFM vane (with your finger) to see what that tells us. IMO that's far better than pulling a hose or jumpering a couple of electrical contacts, because it's easy to overshoot with those methods. When your mix is right, the RPMs will only decrease when you nudge the AFM vane to either direction. Anyway, go for a drive! Enjoy your Z! Recharge, refresh, and return. Stay on track, and all will eventually be well.

I doubt it. He'll probably be impressed that you're learning to do this stuff yourself.

Hey, congrats! I'm glad yours were easier than mine. Mine were a nightmare. Yeah, just go to your nearest Ace or True Value (not kidding). You'll probably find some allen-head stainless screws there of pretty close to the right size. If they're too long, you can cut them down. Just be certain to clean up the threads on the end with a file before installing.

Also check the fuel/air separator. Mine had a crack in a solder joint on one of the nipples. It wasn't enough to smell, but it was enough to wrinkle up the black paint on the thing.

Brian, you're making me blush. However, the truth being told, carbs puzzle the @$#% out of me! I mean, I know how they work in theory, but all those tiny little passages in a Holley double pumper, for instance... geesh! So I feel pretty lucky whenever I manage to keep a carb'ed engine running.

Argneist, an experienced mechanic might be better at removing stubborn screws, which is not to say that you shouldn't do the job yourself. (I'm just telling you.) After taking on a big engine project, you'll get experienced pretty fast! Just be slow, careful, and thoughtful, because mistakes can cost you -- money, time, frustration, emotional drain. If your injector screws are frozen, I suspect your engine hasn't had any major work before. In that case, your manifold nuts/bolts/studs should be well frozen too. I can tell you it might be a long and frustrating process to R&R the intake and exhaust manifolds. (You do both at the same time.) You can read all about my saga in my "purs like a kitten" thread. How hard? Well, let's just say when I managed to break that last rusted/corroded/almost-not-there stump of a stud loose, we went out to dinner to celebrate. That said, the next time (if there's a next time) will be a snap, because my threads are all clean and lubricated with nickel anti-sieze, my hardware is all fresh and new, and the whole assembly won't have 3 decades of corrosion on it. I suspect I could R&R the manifolds in a long afternoon (or at least a day) now.

^^ What Steve said! The FSM and many Z people say the easiest way to remove the injectors is by removing the injector screws and pulling the entire rail. However, I see no reason you can't cut the injector hoses, remove the rail, and then work on the injectors individually. This would give you more working room. When I installed my new injectors, I first populated the rail and then tried putting the assembly in as a unit. I found that was about as easy as putting a cat in a sink of water for a bath. I then pulled off all the injectors, installed them individually, and then pushed the rail barbs into the line of hoses. Much, much easier. When removing the screws, keep the screwdriver perfectly straight. First tap the bit into the recess with a hammer. (Don't get carried away.) Then apply very firm pressure while you turn. If you end up stripping the head, you can drill it off and pull the injector out over what's left of the screw. Then you can deal with the remainder of the screw with another long soaking in PBlaster and then a SMALL pair of very new/sharp vice grips.

Yeah, my meter reads about 15.5 V when it really means 14.5V. I didn't know they were adjustable, Zed. I wish I had known that when I had it pulled for dash light replacement. Anyway, yeah, you have to use an accurate multimeter to do the measurement. You can buy one for maybe $10 at Radio Shack. Running voltage should be around 13.5 - 14.5, as I recall. You don't want to get much higher than that, or you'll damage the battery. Edit: Sort of agree about the avatar. I know you're not THAT large, or else you wouldn't fit in the Z.

When I bought my Z, the PO had just replaced the shifter boot, and it did feel dorky and cardboard-ish. It also stuck up too high. It had a seam around the base that I couldn't really understand. So I settled the strange seam down in the recess, pulling the entire boot down a few inches. After a bit of usage, it feels just fine. I don't notice it anymore, and I think it probably feels like the original boot I had on my '75 that I bought in '82. It would probably be easy to make a shifter boot (and emergency brake boot) in leather. You just need to find a heavy machine. At some point in the intermediate future, I'm going to try making myself some leather seats, and I'll probably do the boots then too. (I recently acquired a heavy industrial sewing machine.)

I don't understand your last post, but a squeezed boot shouldn't affect the engine's running. It's still possible you have a vacuum leak between the intake manifold and cylinder head. (I had a big one.) I finally verified I had no vacuum leaks with what I call my "yogurt cup test." Very simply, remove the AFM, and stuff a yogurt cup onto the boot, plugging air flow. Then pull off the brake booster vacuum line, and put a short, clean hose on it. Put the other end in your mouth, and blow. You'll be able to blow a bit of air into the manifold, pressurizing it. If you blow hard enough, you'll pop the yogurt cup out of the boot. At some fairly pressurized point, just stop blowing, and hold the pressure with your mouth. If the pressure takes maybe 10 sec to leak down, your intake system is probably pretty tight. To establish a frame of reference, you can pull off a small vacuum line and repeat the test. You'll hear/feel air escaping much faster. One small, completely open vacuum fitting is enought leakage to affect engine operation a little bit, but not dramatically. Then if you're SURE of all of the following... *NO vacuum leaks *correct fuel pressure *correct timing *a good distributor without the common frozen breaker plate problem *all your sensors within spec, as measured at the ECU connector *AFM within spec ... then your ECU components might have drifted, resulting in too short an injector pulse (hence lean running and intake backfire). More and more of us are discovering this. The cure for this condition is to add resistance in series with the temperature sensor. You can look up my "purs like a kitten" thread to read the long saga that led me to this fix. The coolant temp circuit adjusts the length of the base pulse, so this correction takes place over all operating conditions. In my own case, I estimate I was running with about 25% too little fuel. I corrected this condition by adding about 2.6 kOhm in series with the temp sensor. Cozye did the same thing, but he wasn't running as lean as I was and added a bit less resistance. We both used variable resistors, so that we could adjust and fine-tune our mixtures. I added the 20-turn variety of trim pot. Ideally I would have used a 5kOhm trim pot, but I didn't have one in the 20-turn variety, so I used a 10k pot.