FastWoman

Yeah, I bought the Bosch injectors in the early 80's for my '75 Z, and I bought the Standards somewhat recently (1.5 years ago?) for my '78 Z. I definitely had more money to spend/blow back in the 80's. Geesh, stop throwing rocks already, Wade!!! (Zed, see post #2 for why Wade's chucking rocks my way.)

Thanks! Actually it turned out that way. We kept talking the thing around and discovered that argneist's car was only running on cylinders 1-3, give or take. The problem, which argneist discovered, was that the EGR passage was eroded through to the intake manifold (i.e. bypassing the EGR valve and dumping exhaust into the rear of the manifold). We were all astonished. Kudos to argneist for sticking it out and discovering this weird issue! Oh, the end of the story is that he disconnected his EGR. End of problem!

Glad it worked out! Zed, that's sort of what I was thinking, without running the numbers! Besides that, the PO of my current Z had replaced ONLY ONE leaking injector, and I think I recall him saying his part price was around $150. It was a Nissan dealership that did the work and supplied the part.

I'm sort of surprised. I bought a set of Bosch injectors for my '75Z back in the early 1980's for something like $65 each -- dealer prices.

They're worth a whole lot more than the $200 you're asking for the set, and I suspect someone will be willing to pay you a fair price! If I recall correctly, at least triple or quadruple that price would be more in line. More accurately than that? I don't know. Please, nobody throw rocks at me for spoiling such a good deal!

You should be getting one injector pulse per engine revolution. Are you getting more than that? Try hooking up a timing light and a noid light. The noid light should flash twice as often as the timing light. This will be easiest to confirm when you're cranking the engine.

You're quite welcome! I'll be watching with interest as you recalibrate!

My guess would be a broken or rusted fuel pickup. It happened to my first Z, which was also a '75. I would get to a half tank, and then I would be out of fuel. I don't recall having heard buzzing sounds, though.

The intake boots usually crack inside those accordian-like folds, so I'm skeptical the tape is covering a crack. But you never know. Pull off the tape and have a look! The little doodads in the second photo are called "magnet valves." One of them turns the vacuum on and off to your HVAC control systems. It sometimes goes bad, so people just bypass it without any ill effects. The other one switches vacuum on and off to the high idle actuator on your throttle linkage assembly. It's the thing mounted to your intake manifold with the hook on the end of it, which pulls against the tab on the side of the throttle linkage. This system is actuated along with the compressor when your A/C kicks in. Mine is fussy as hell, and it's almost impossible to adjust well. If yours doesn't work, I wouldn't worry about it too much. The engine can pull the compressor at a normal idle just fine. There's a diagram of how all the HVAC control tubing is connected in the heating/AC section of the FSM.

Yeah, there are very few unmolested AFMs. Most of us have to re-molest them to get them back to normal. As long as the plastic cover seals (with silicone caulk), it's good. It should be a fairly durable part, so if there are some chips missing, it might not mean the cover is breaking apart. Perhaps someone mucked it up by prying on it with a screwdriver. I would recommend cutting the caulk all the way around with a razor blade. Then the cover should pop off with much less effort. I have no idea whether MSA cares about the plastic cover, which perhaps they replace anyway. That said, it shouldn't be too hard to re-molest and put right.

So I'm driving the back roads and see a very nice copper '78 Z in the middle of a field with a "for sale" sign on it. I pull over and knock on the door, asking to see the guy's Z. He shows it to me. Throughout the course of the conversation, I realize he is trying to sell a 1978 280ZX. I keep trying to explain to him that there is no such thing -- that his car is a 280Z. He finally instructs me to look at the "Z" on the logo, which has a hash through the middle of it ("X"), making it a 280ZX. I explain that the letter "Z" is crossed in some countries to distinguish it from the number "2." He then shakes his head and tells me his insurance company insisted his car was a ZX and not a Z, explaining about the crossed "Z" on the emblem. All along, they had been charging him higher insurance premiums for his 1978 280ZX than they would if it were simply a 280Z. The snakes!

For the first time EVER (and I've been driving 280Z cars since the 1980's), I've fueled up my 280 with 87 octane. It runs fine. Why 87? It turns out I can now buy REAL gasoline (no alcohol) at a gasoline distribution depot near me. It cost me about $3.80/gal, about $.65 higher than the gasohol. Unfortunately they only have the 87 grade without alcohol.

Ok, you're definitely running a bit lean, then, at least at idle. And yes, 1100 is a bit high, but you would simply adjust it down with the idle adjustment screw on the top of the throttle body. That's not really an issue. You might try a little experiment now. Pop open the little black plastic cover on your throttle position switch. You'll be able to see the contacts inside. When you open the throttle all the way, there will be two contacts that close together. Figure out which two pins those go to on the connector that connects to the TPS, and insert a wire to short between those two pins (i.e. with the connector disconnected). This will give you full throttle enrichment. Dial down your idle speed as needed. Now take your car for a short drive, and see how it feels. If it runs better, that would be further confirmation of a lean condition. The most common cause of a lean-running condition is vacuum leaks (usually at least a few of them). Also carefully check the boot between the AFM and throttle for splits. Try my "yogurt cup test" to trouble-check the entire intake all at once. http://www.classiczcars.com/forums/thread44365.html ... around post 6?

It's a very good comparison. Based on the exhaust flow rate, it sounds like you're running lean, not rich. It might be there are no water droplets because it's so HOT. Perhaps in cooler weather your exhaust would be spitting. The best way to diagnose your mixture is to remove the black plastic access cover from the side of your AFM and to lightly finger the counterweight to slightly open or close the AFM vane. Lightly opening it (by turning it counterclockwise) results in a richer mixture, and lightly closing it results in a leaner mixture. If your mixture is right, fingering in either direction will drop the engine RPMs. I would bet that if you finger it in the CCW direction (richer), your engine RPMs will pick up quite a lot, indicating that you're currently running quite lean.

Your heating and air conditioning controls are all vacuum driven. There's a little vacuum hose that runs from that pair of magnet valves on the passenger wheel well, through the firewall, and to the mode selector switch (e.g. off, vent, a/c, heat, etc.) in the dashboard. If that leaks or doesn't have vacuum, the vacuum valve on your heater core will never open. That's probably why you don't have heat. Fortunately you don't have to worry about that for a while! If I'm not mistaken (and I might be), vacuum isn't needed to run the A/C. You may as well cap off that little vacuum fitting right beside the larger power booster vac hose near the backside of the intake manifold, until you get your engine running right. Then you can deal with the heating system later.

Congrats, Tiffanie! I think your dad would be proud of you! Very cool car, indeed!

Yes, the engine needs to warm up. Try this: With your car warmed up and idling, hold a clean paper napkin behind the exhaust pipe for a couple of minutes. Does it get speckled with sooty little water droplets? If so, your mix might be too lean. Also, does the exhaust seem to be blowing rather hard, compared to a properly running car's exhaust? This, to me, is the most telling feature of a lean mixture. A lean-running engine will blow like the exhaust of a vacuum cleaner.

It doesn't make sense to go replacing parts on these old cars without knowing whether they're bad or out of adjustment. Parts are in short supply, so trashing a perfectly good part that's not in aftermarket production would be a sin. The BCDD is not in aftermarket production, and many/most of them do not work. If you have a working one (which it sounds like), please enjoy it, and don't trash it! It merely needs some adjustment (see the FSM) for the idle to kick down a bit faster. Without the BCDD, the idle just plummets as the throttle slams shut, and the idle speed will overshoot, possibly causing stalling. The BCDD gives you a more refined drop in idle that prevents idle overshoot and smooths your shifting. And if you don't want your BCDD, please send it to me! I'll gladly pay the shipping! Your black plugs could mean either that you're running rich or running really lean (which can cause incomplete combustion or a partial misfire). You can distinguish between the two conditions by the character of the exhaust: Rich: Sooty exhaust with a flow rate similar to that of a normally running engine. The fumes will burn your eyes a bit. Extremely lean: Exhaust doesn't look as sooty. It blows hard, much faster than that of a normally running engine. There will be random misfires (hard exhaust puffs) that spit small droplets of sooty water. FAIW, there seems to be an issue with the 77/78 (particularly 78?) ECU, such that it drifts leaner over the decades. This has happened to several '78 models on this forum, including mine. It's possible the '76 models share this problem. I believe the '75 system is made by Bosch, and the '77/'78 is made by Hitachi. I don't know about the '76, though. Anyway, if yours has drifted, there's a remedy for that. Let's first find out whether you're running rich or lean: Can you describe the exhaust? What's your engine vacuum? (Do you have a gauge? They're cheap and very useful.) If you pull off a small vacuum line, does your idle rise or drop? (You can also crack your oil filler cap, but just THE TINIEST bit). What happens if you pull the vacuum line off your fuel pressure regulator and cover the end of the hose with your thumb? -------------------------- As a general approach for getting these engines right, you should first look for the most obvious stuff that plagues most of our engines: 1. Rotted vacuum lines (You'd be smart to replace them all -- very easy) 2. Split boot between AFM and throttle body. 3. Other vacuum leaks (e.g. intake gasket). I've described a "yogurt cup" test that works pretty well. 4. Corroded electrical connections 5. Frozen breaker plate in distributor. (Remove cap and rotor, and try rotating the "guts" of the distributor CW by hand. Does it bind? Put a tube on the vacuum advance, and suck on it. Is it air tight?) 6. With the vacuum advance disconnected (and something inserted into the tube to plug the vacuum leak), check the timing. The specification in on a sticker on the underside of your hood. (On the '78, it's 10 deg BTDC, but many of us run a few degrees more advanced. Mine is at 13.) 7. Check/adjust your valve lash. I've listed these in order of ease and importance. Fortunately the most import ones (listed first) are generally also the easiest.

Well, the vacuum reading and the plug reads are the final tests of how your engine is running. On a well worn engine with good compression (like mine), engine vacuum at idle should be 18-18.5 in Hg. An ideal reading would be maybe 19. A marginally acceptable reading might be 17. This mostly tells you how good your mix is at idle, although larger deviations from this mark would also indicate something about mixture under load. There's a mixture adjustment screw at the base of the AFM near its outlet, concealed beneath a small plug. It doesn't really do much on my AFM, but it might on yours. Clockwise would be richer and CCW leaner. Then your sparkplugs are the ultimate reading on mixture. Run your car around for a while, and pull them. They should have a nice mocha coloration on the insulators. White would be too lean, and black would be too rich.

^^^ better idea

Hi Johnny, I seriously doubt your water temp sensor could have that much crud built up on it. If it does, then you have bigger problems (clogged water passages and such). Even if it were covered with crud (which I doubt), it shouldn't affect temperature readings. Of course the crud on the electrical connections is another matter. Electrical connections do get crusty and do require periodic cleaning. The air regulator wouldn't affect richness. It only affects idle speed. To semi-bench test it, pull the hoses off of it when your engine is cold, and look through it with a mirror. You'll see a little baffle that should be partially open. Now turn on the ignition without cranking the engine, and continue looking through the regulator. You should see the baffle slowly close as the bimetal strip is electrically heated. If this happens, then the air regulator is doing its job. I hope that helps!

PS I enjoyed your photography. Seems we have more in common than a love of often cantankerous Z cars: www.graphic-fusion.com

"BAD" -- Well, I'm glad it's solved. As far as the rich running is concerned, likely culprits are the TPS, CTS (too high a resistance or a bad connection), CSV (possibly stuck open, even if not connected), molested or damaged AFM, resistors added in series with the CTS and buried in the wiring harness (e.g. like on my car), FPR (regulating too high)

Interesting! I wonder whether you still have drop resistors, or whether someone simply removed/bypassed them, thereby overloading the injector driver circuits, as Wade suggested. The drop resistor assembly is located beneath the brake master cylinder. It would be a good idea to measure the resistance from + to each of the ECU's injector connectors. I forget the resistances of the various components, but I think I recall the drop resistor and injector both being about 2.5 ohms (each -- i.e. 5 ohms in series). I could be wrong about this, but I think all you need to confirm is that they're somewhere in the general range of correct. I'm going to throw out another guess: Maybe your alternator is going bad and blowing out your ECU. How is your system voltage? Is there a noise suppression capacitor connected between the alternator + post to ground? Of course since your car isn't running, it's hard to determine these things. Maybe you could pull your alternator and have it tested at your local auto parts store. If something is killing your ECU, I would think that's a likely cause.

I think you've covered everything. Your pin 10 seems to be the + supply to the ECU, and you've confirmed the ECU grounds. Your pin 1 is good, and yet when you cycle it between +12 and gnd, there's no injector pulse. I'd say your ECU is dead. I don't see any other possibilities, although others here might have some other ideas.