FastWoman

Problem is, I'm afraid to advance my timing any further than the spec 10 deg BTDC. I still get infrequent intake pops, unless my AFM is adjusted AT LEAST out as far as it is now. The 36 mpg tells me I'm running really lean -- to be confirmed very soon. I may ultimately advance the timing a tad beyond spec, but not until I have the mixture right. BTW, you forget I don't have Nissan injectors installed right now. I'm running brand new Sorensen injectors. They were sold to me by an Ebay vender who sells 280Z stuff and were represented as being compatible with the car. The hoses were a bit short, so I was a bit suspicious. Perhaps my next step should be to pull the fuel rail and flow test the little guys. Just like you, I found the AFM's main spring tension about right at the original setting, per the article on Atlantic Z. I've checked/measured everything else on my EFI. As far as I'm aware it's not an ECU issue, because my spare ECU works the same way. The easiest thing for me to do right now is to flow test. If my injectors, fuel pressure regulator, and fuel pump are delivering to spec, then I'll be suspicious of the pulse duty cycle delivered to the injectors by the ECU and will start looking for cold connections on its PC board. Anyone know what the spec flow rate is on these things?

I'll try that, but I think I'm not to that point yet. I'm definitely nowhere near rich. I took an easy, 45mph drive down the Colonial Parkway for a total distance of 36 mi and consumed EXACTLY 1.003 gal of gas (topped off to the brim). If I remember my math correctly, that would be about 36 mpg. I think reading the spark plug would almost be a formality at this point. I'll do that tomorrow when the engine is cool and the sun is out. I'm guessing white and chalky. Wha'd'ya bet? So maybe the richer setting I had earlier was the more correct setting. The only problem is that with the spring tension so low, the AFM meter would peg out before the peak of the power band, and then I'd be running lean at WOT. I'm guessing there's something amiss with my fuel pressure and/or my (Sorensen) injector flow rate. I'll see if I can scrounge up a more accurate pressure gauge. Maybe the solution is to go with the flow and to get that adjustable fuel pressure regulator to do my mix adjustments? The car took off like a bat out of hell with yesterday's adjustment.

Well, second test drive tonight. I backed the AFM main spring to 8 teeth richer than where it was originally set, and I advanced the idle mix screw quite a lot to 6 full turns CCW from closed. The idle mix screw didn't seem to do much of anything. Clogged port? (To be tested.) I lost 1 in Hg -- now at 18. However, I'm a bit more comfortable overall. I'm going to focus on mileage and plug appearance. I have a fresh plug in #1 and will read it at the end of the test drive. I'll know very fast if I'm running rich. Just a hunch: Perhaps the new injectors don't flow as fast as the OEM ones? Perhaps I need higher fuel pressure to compensate, rather than an easier AFM spring? Wish me luck. :-)

First test drive: LOTS more power, but some missing at WOT. I think I might be running a bit rich, although I don't see any black smoke or anything. I'll be trying the rough calibration (using coke cans) described on the Atlantic Z site and then will be balancing out the idle with the idle mix screw. With that starting point, I'll take a very long test drive, so that I can compute the mileage and read the plugs.

I agree with Steve! Your first post on this forum sounds a bit like, "How can I steal all your cars?" Even if you're an honest person, which you probably are, any thief can search this forum for "security" and find out how to steal our cars. Security systems are something I don't even discuss in private with trusted friends -- because they tell trusted friends, who tell friends, and so on, and so on... That said, I think the best deterrent I've seen is commercially available. It's a device that fogs the interior with smoke and mace, and sets off strobes and sirens when triggered. I'd hate to have the thing false-trigger, though!

Behind the rubber plug? There's a rubber plug? Hmmmm... Not on mine. Just the screw, which is roughly flush with the housing (i.e. so there would be no room for a plug). Should it be screwed in quite a bit more than that? Perhaps that was an adjustment the PO made? (I was hoping that adjustment went unmolested.) Grrrrrr.... Well, I'll do the test drive tomorrow. I'm guessing I'll be too rich at half/full throttle and will indeed need to wind up the AFM again -- and advance the idle mix screw quite a lot to richen the mix at idle. Anyway, one thing is for certain: Given the right fuel/air mix, the engine runs fine. (Same in your case, Cozye.)

I guess this project took longer than I expected. I took my time and did it right. Yeah, I've been looking for a spare AFM. It's actually the last piece of the EFI system that I don't have a duplicate of -- well, that and the intake boots. (I used my spares in the rebuild.) BTW, special thanks to you, Ztrain! You hung with me through thick and thin. Much appreciated!

It's dark!

Cozye, I'm more or less finished with my engine. It runs great now. Check out my "Purs like a kitten" thread. The final step that got my engine running normally (bringing up the vacuum, smoothing all the misses at idle, stopping the light backfiring issue) was my adjustment of the AFM. I had to enrichen the mixture by TWELVE TEETH! After I was finished, I had a vacuum of 19 in Hg, with no misses and a much less labored exhaust sound. When I was finished, the engine RPM dropped roughly equally with a push of the AFM vane in either the open or closed position. I'll add that I was doubtful about needing to enrich the mixture, because I could smell unburnt hydrocarbons in the exhaust. However, I think the unburnt hydrocarbons were from the misses. I'm guessing that a cylinder would occasionally miss because of too lean a mixture, and the unburnt fuel would enter the exhaust. Then it would ignite, burning inefficiently, creating a hard puff. I would smell what was left of the poorly burnt fuel. Even though I kept enriching the mixture, I didn't really get fumier exhaust. If anything, it smelled cleaner as the mixture got richer. Go figure. Anyway, the AFM adjustment seemed to be the magic juice for my engine. Maybe it will work for your engine too. Good luck!

... with a bad attitude! I just wanted to let y'all know I got my engine back together. It's all cleaned up, checked part by part, refurbished, refreshed, painted pretty, reassembled, double checked, triple checked, etc. It started on the first try, but it ran much like it did before -- exhaust blowing hard and puffing with frequent misses. Engine vacuum a bit lower than before I started -- about 11 in Hg. I had occasional hesitation upon revving, with occasional light backfiring. I had resolved at that point, having gone through the whole system, to make my final adjustments at the AFM... which is what I did. I first gave the vane a gentle push towards the open/enrichen direction. Engine speed and vacuum picked up A LOT. I dropped spring tension by two teeth and repeated. Higher vacuum this time, but the engine still picked up when I pushed the vane open. I adjusted by another two teeth and repeated... and repeated... and repeated... TWELVE teeth from where I began, I had a normal engine vacuum (19 in Hg), the engine was running very smoothly, and the exhaust was no longer blowing hard and missing. It sounded like a very content kitten with an attitude. The weird thing is that the AFM appeared to have had the factory caulk blobs on the set screws. I had assumed it had been unmolested. On the other hand, I knew it had been opened, most likely by the PO. He used clear silicone caulk everywhere on the car and had the same caulk sealing the cover. The silicone caulk on the set screws appeared to be a whitish caulk, so I'm guessing it wasn't his. Did the factory use silicone caulk/sealant/adhesive to blob against the set screws, or was that the handy work of a mechanic along the way? Anyway, the spring was wound up pretty tight. It definitely felt a lot lighter when I was finished. A gentle push is all that is needed to open the vane now. The test drive is tomorrow. (Caulk is curing tonight.) I'll take pictures for y'all to show off the engine. It came out quite well, I think. Only the top is painted. Cylinder head and block are as they were. I painted the intake manifold to resemble a '75 intake -- by blacking out the webbing. I think it's much more attractive that way. I have a bit of touch-up painting to do, as engine assembly is frought with nick, scratch, and bump hazards. Anyway, knocking on wood, I think I'm in the clear now. Thanks for helping me along on this project! I don't think I could have gotten to this point without the moral support and technical advice of my fellow Z enthusiasts. Peace, Sarah

Here's an idea: Adapt an air hose to the drain plug hole. Shoot compressed air into it.

There are some differences in the design of the spare tire well in the hatch floor. The spare tire well is shallower in the '78, and the '78 tank snugs right up against it. For this reason I don't think a '78 tank would fit an earlier year of Z.

I had a BMW Z3 that had sat up a lot before I bought it. It missed lightly at idle just like your engine, although vacuum was normal. I did a couple of flushes with Gunk to dissolve out the varnish, and that freed up the valves. It purred like a kitten thereafter. I'm currently working on similar issues on my own '78 Z. I'll let you know if I discover anything, but my approach is a shotgun approach at this moment. I've disassembled and checked the entire fuel/intake system and manifolds, and I'm currently reassembling. I had some obvious intake leaks, and my injectors were very worn. I'll know very soon whether new injectors, tight manifolds, cleaning and lubing will have solved my engine's problems.

cozye, there aren't really any wear and tear parts on the throttle. The butterfly shaft runs through ball bearings. I just took it apart, cleaned it up, painted, lubricated, reassembled. Hutch, just get a can of carb cleaner, and shoot it through the air bypass pathway (i.e. where the idle adjustment screw inserts). Also remove the adjustment screw and spray down the hole. After you clean out those passages, replace the screw, and don't screw it in very far. See if you get a high enough idle with the passage wide open. If not, then there's something else wrong.

Enrique, there's a lot of irony in your last post, which shows absolutely no information about which model(s) of Z YOU own! Just funny, that's all... ;-)

Do you mean it idles too high or idles too low now? Could be the air regulator. Pull it off and look through it. You should see a half-moon shaped diaphram, as diagrammed in the FSM. Give it a wiggle with a small screwdriver to make certain it's not frozen in place. Could be that the air flow meter is stuck. Check the metering vane to be certain it moves freely. Also try cleaning the electrical contacts inside the black box on the side. Careful, they're delicate! Also check to see whether the AFM is damaged. The '75 model didn't have a backfire relief valve in the vane, so it was prone to damage. They fixed that problem in subsequent years, but I had a problem with my '75 many years ago. A hard backfire had apparently bent the vane, causing the engine to run rich. I carefully tapped it back into shape, leaning up the mixture considerably. Obviously check that the air bypass port in your throttle body (where your idle adjustment screw is found) is not plugged. Be aware that it's not like adjusting idle on a carb. A fraction of a turn won't do much of anything. You'll be making your adjustment with even a few turns. I just rebuilt the throttle body on my '78, and before I pulled it apart, I noted the position of the idle adjustment screw. It was 5 3/4 turns CCW from fully closed (screwed all the way in). Note that there is also a stop for the butterfly that would have a larger impact on idle speed, so my normal idle screw adjustment might be nowhere near what yours should be, but at least that 5 3/4 turns should get you somewhere in the ballpark. Good luck!

As others have said, not particularly hard. You'll need someone to help you. Removing the interior trim to get to the fuel/air separator was a bit of a hassle. You have to remove almost all of it (the pieces across the top, tail lights, quarter window, and then quarter panel). You also have to pull off the gas strut briefly to pull that last piece of trim, at least in a '78. Might not have to in an earlier year. Undo all the lines first. When you drop the tank, lay it down on your tummy, and have a friend help you pull it off of you. When you reinstall, put the filler neck on the tank first, and have your friend guide it up the hole and shove it over the metal inlet neck. Easy. Get your 5/8" fuel line either from a tractor supply or by mail order from Hampton Rubber of Hampton, VA. (They don't usually do mail order, but they'll accommodate you if you call them and ask nicely.) FAIW, your filler neck might be OK. Mine is made from some indestructable rubber like neoprene. It might be the fuel vent hoses at fault. Also inspect the paint on the separator for any tell-tale signs of leaking welds or solder joints. Mine had to be repaired. Have fun. It's not a hard job but does take some time.

Oh man! Reminds me of when I got my '75 Z all painted up nicely, new rims, looking sharp. I was at a light with a Volvo 240 wagon in front of me. When the light turned green, the kid in front shifted into reverse and "peeled out," apparently to impress his girlfriend. (I'm guessing she wasn't very impressed.) He ate my hood, headlight buckets and lights, signal lights, and air cleaner. The bumper was fine. Fortunately parts were easily available (not yet an antique), and he had a good insurance company.

Zed Head, 64psi should still be safe. It's still not really that much pressure. I think these fuel lines are rated at something like 500 psi. Newer fuel injection systems run on much higher pressure too -- maybe up to 140 psi. Blocked injectors and bad fuel pressure regulators are often blamed for things like bulging fuel injector hoses and fuel rail leaks, but these things are more attributable to rotted rubber, corrosion, etc.

What David said. Spray some starter fluid in the intake, and see if it at least runs a few seconds (even if badly). You can spray it directly into the intake manifold through a vacuum fitting. That will rule out ignition and general engine issues. If it won't fire up, it's probably ignition. If it does fire up, your problem is probably fuel. If it's fuel, make sure your injectors are being energized. There should be a voltage across them once per engine rotation. Just unplug one of the injectors (by first removing the wire retainer clip), and put a multimeter across the connector. You should get a blip once per engine rotation. The problem(s) could be almost anything, but that should get you started.

A bad regulator won't cause your fuel hoses to blow/spurt. Your fuel pump will generate over 40 psi, but has an internal relief valve. In other words, if you completely block the fuel flow, your pressure will be a safe 45-ish psi.

Dave, Koalia, the one "click-clock" sound sound when the turn signal is engaged is probably an indication that the tail light circuit (including flasher) has been energized. That's why I think it's the flasher. However, it's also possible there's inadequate current to that circuit -- perhaps from corroded connections in the hazard switch. (Dave's our switch guy, so his hunch is perhaps better than mine.) I still believe strongly in the LED conversion, BTW! The more that can be done to reduce current demands on our switches, the longer our switches will last.

Very confusing thread! I'll just offer the following: (1) This is a Z forum, not a ZX forum. There's also a ZX forum on classiczcars.com, where you might find more ZX people. Most of the folks here seem to be familiar with the 240Z, and there are a few people like me who know the 280Z. However the ZX is another generation with only a few things in common with the Z. I think most of us wouldn't have a clue how to answer specific wiring questions for your car. (2) If it's any help, the wiring from the output of my '78 280Z (last year before the '79 280ZX) was rather inadequate out of the factory. The wire gauge is too small (maybe 10 ga to carry 60 A), and the fusible link that protects the circuit melts down at 80A. Crazy! Moreover, the wire is joined at numerous points by crimp connections in the wiring harness. When these corrode, they can heat and char. (My alternator wiring had already gotten rather toasty.) I replaced my alternator wire with much heavier wire. (3) In answer to your "where does it go" question: Our cars MAY be vaguely similar in this regard, so... I believe the output from the alternator should go to a fusible link, and then the other wire from the fusible link should go to the battery. If memory serves, the white wire goes from the alternator to the fusible link, and the white wire with red trace goes from the fusible link to the battery. (It could be the other way around, though. Look at the wire coming from the alternator.) And of course you're going to have multiple fusible links, so I couldn't tell you which one is which. And finally, your car is a ZX, so I don't really know if any of this applies. But maybe that will get you started. Good luck!

You wrote: "Then there was a pop, and smoke billowed up from under the header." i.e. from oil spraying on your header? That would certainly be an indication of a blown head gasket. Do you see oil on the side of your engine? I can't give you any good advice, as I've never dealt with a head gasket. All I can do is to wish you good luck and to say that I, too, have found these engines to be very tough/durable.

What sblake said. The big screw with the spring atop the throttle body sets the idle speed. It regulates how much air bypasses the throttle plate. There's only one screw adjustment for fuel/air mixture, just below the exit port on the AFM. It's factory adjusted, and it's not recommended you adjust it, although it might have been adjusted by someone else. It regulates the air bypass around the air flow meter and, as far as I can tell, is used for tweaking the fuel/air mixture at idle only. CW would probably richen the mixture, and CCW would probably lean it (opposite from the mixture adjustment screw on a carburetor).