FastWoman

"gasoline flashing to vapor before it can get through the orifice." ^^^ I think this is the most likely explanation. If the injector is well above the boiling point of the gasoline at the operating pressure, it will take a certain amount of gasoline vaporization to cool it down to the boiling point, and all of that amount will have to pass as a vapor through the jet. When the hot restart stumbling resolves, it resolves SUDDENLY, as though there is a quick transition from injecting vapor to injecting liquid fuel. The cylinders catch, and then all is well. It is for this reason I am skeptical a fix is possible through intelligent control by the ECU. I would think the ECU would have to detect stumbling, apply its corrections, and then abruptly cut off those corrections when stumbling disappears. But some cylinders run rich, while others run lean. An O2 sensor is unlikely to distinguish between rich stumbling and lean stumbling. Maybe you can do it, but I have my doubts. Sadly, I think the only "real" solution is to find a way to cool the injectors, as with the ugly ZX blower.

I'm surprised you had enough carbon to bridge the electrodes! Was there this much carbon on all the plugs, or just some? With the hot restart problem, the theory (or at least mine) is that some injectors are spraying fuel, while others are blowing fuel vapor. This could happen with or without an underlying rich or lean condition. I suspect your coolant temp sensor connection became faulty, causing an extreme rich condition, resulting in the extreme fouling. Whenever I have a hot restart problem, the car fires up without difficulty, but it seems to run on 2 cylinders until I can get past the "theoretical" fuel vapor, which is usually when I get to the road and punch the accelerator. An extreme lean condition can result in fouling if there's incomplete combustion. I'd say if your engine is running lean enough to backfire, it's lean enough to foul the plugs. It's uncommon, but this is exactly what happened in my own Z. When I richened the mixture, the carbon fouling problem was gone.

Lenny, I strongly suspect fuel pressure is the culprit with the hot restart issue. Engine compartments have been getting smaller and more cramped, and they've even become more insulated, so I can't imagine that heat soaking has become any less of an issue over the years. But with the higher fuel pressures of modern cars, the fuel is less likely to boil. I would think the solution is to change out both the pump and the FPR for a higher fuel pressure and to make adjustments as required with the Hellfire tuning. Anyway, I might be one of those people who discussed fuel rail priming with you. I know a few of us have tried it. Trust me that no amount of priming seems to eliminate the hot restart issue. I think that's because the injectors themselves are hot enough to flash any fuel that flows into them, so they are initially injecting vapor.

I hope I can remember the name!

Tomo, why not just wear period clothing? For a later model Z, a polyester leisure suit and elevator shoes would be great. If you could grow out a cheesy moustache and chops, all the better. For an earlier model, you could break out a pair of old bell bottoms.

Lenny, apparently my mind had gone somewhere else. Inexplicably, I thought you were proposing a pigtail for the additional I/O lines, not for the USB link. In the words of Emily Litella, "Never mind."

"So engine wise, the 280 is better?" That depends on whether you like carbs. Some people love them. I hate them. For overall drivability, yes, I think the 280's fuel system is better. (The engine is mechanically about the same.) The only caveat is that a hot restart after about 20 min of sitting can be rough, depending on the fuel you use. After another 20 min, the problem goes away. It's a known issue with the EFI in these cars. However, if you have to start your car hot, it will start easily enough. It just won't run very well until you get started down the road.

Jacco, The 240 is a better track car. The 280 is a better GT. Most examples of each will have their fuel system issues. The 280 has an early L-Jetronic EFI, which is an open-loop analog system. Once you get it working correctly, it will be much more reliable than carbs. However, it can be an aggravating system to learn and to get working right. It won't help you by giving you fault codes. Superlen (on this list) is currently working on a drop-in replacement digital ECU that will modernize our EFI systems. The 280 also has electronic ignition, vs. points in the 240. Finally, the 280 has a heavier and better alternator. Personally I like the 280. It was the cool sports car of my generation. And yes, I even love the horrible bumpers!

Sooooo.... What'cha doin' with the bumpers, besides removing them? Are they in good shape?

Lenny, would a DB25 connector on the shell hold up to the rigors of an automotive environment? That would be more civilized than a pigtail. Perhaps some sort of Molex connector would work better. FAIW, anyone wanting to cut a hole in the kick panel should probably back it with some reinforcing material. I think the kick panels are ABS, and there's black ABS cement in the plumbing isle of your local hardware store. I've not tried it for repairing interior panels yet, so I can't report how well it works. But I bet it's the stuff to use.

Seriously, I wouldn't cut any holes in those interior trim panels. They're rather prone to cracking.

Yea! Another '78! Nice looking car! And welcome!

NICE! Love the colors. I also love the wheels, though they're certainly difficult to keep clean. True spoke wheels were EXPENSIVE back when I was considering them for my '75 Z. But they're certainly not practical for use on a DD.

Lenny, FAIW, the '78 kick panel has a rectangular hole through which the ECU's green P/N sticker is visible. If you do decide to put an LED through a hole in the case, that's the place to do it. Also if you want to be super-polished, you can put your company logo there, and it will show through the rectangular window. That could look pretty slick!

The lovely thing about a Z is that it looks awesome in any color or patina! Congrats!

Hi Lenny, If I could lend you an AFM, I would. However, I don't have a spare. I like the idea of using OBD2 codes (if I understand correctly). However, the ultimate interface, requiring no dedicated reader, is the smart phone app. There you'd see not only the OBD2 codes, but their translations into English. How cool is that? Oh, and the check engine light? Definitely. Most people treat theirs as though it says, "Please ignore me. Please ignore me. Pay no attention to the glow from your dash." Some mechanics even tell their customers to ignore the finicky thing because the ECU won't stop throwing a code. However, I've never seen a properly functioning engine that throws codes just for the heck of it. I like having a CEL, and I carry around a code reader in my only post-1996 vehicle. (I've got 1978, 1992, 1994, and 2009.) I'll make one recommendation, though, for those who do ignore codes or for those who have already noted a less serious problem and can't fix it for a while: You might want to let the user temporarily disable a specific code, so that it will no longer trigger the CEL. That way if anything ELSE goes wrong, he/she will be alerted to it. Also, I don't know if there's a code for low battery voltage, overheating, or low oil pressure, but it would be great to be able to set up those items to be monitored, so that if an input strays outside of a "safe" range, the CEL will light up. Heck, I'll probably even wire mine to the seat belt buzzer (equipped with a "silence" switch, of course)! That will give it a marvelous Cold-War-era feel, adding a bit of entertainment to my misery.

I got tired of my buzzer and disconnected it. Very easy: Get the thing going, reach up under the dash, and feel for the part that's vibrating. Then pull its plug. Done. That said, I did enjoy the thing for a while. It has a Cold-War-era feel to it, with the buzzer going bzzzzt -- bzzzzt -- bzzzt and the huge "fasten seatbelt" light flashing on and off. It sounds like something ominous is going to happen. I think if someone were to ask me if that was normal, I'd say, "No, I don't think so. It's never done that before... Unless... Wait... Oh no... OH DEAR GOD! GET OUT NOW!!!"

You're not finished yet, bhermes. You still need to do the Snoopy dance around your newly repaired Z! Anyway, congratulations on finding the problem. Here's hoping your next problem is far, far down the road! (BTW, don't be discouraged if another gremlin pops up sooner, rather than later. The more you work through these early gremlins, the more reliable your car will become. Eventually it will be a rock-solid reliable car.)

Mark, I think that's a pretty solid explanation. Fusible links are very, very slow-blow fuses. Perhaps the fire in the RX-7 was from a faster overload. Modern cars don't have fusible links, as far as I'm aware. Instead they have regular fuses.

The interesting thing, to me, is that we didn't lower cars this way back in the day. The fashion of the day, at least for American muscle, might have been to lower the front end a bit and to oversize the back tires, not that I would expect a DEALERSHIP to represent its models this way. And I don't recall seeing any lowered Z's back on the road back then. Which makes me think this might be a fake (not commissioned by Nissan to present to select dealerships). Either that, or the model got squished a bit. (The roofline is wrong too.)

Thinking about a "kids mode," my own kids mode is a defeat switch that nobody can figure out and that only one other person (who also drives the car) will ever know. I mostly have this defeat switch to prevent theft by joy riders, but I recall when one young man in our family, a very green novice sailor, took a small sailboat of ours out in some very rough weather when we told him he couldn't. It was weather not even a very experienced sailor could handle! He apparently flipped the boat as soon as the sail went up, and he screwed up some of the rigging. He's also quite hard on cars. Anyway, with my defeat switch, "no" really does mean "NO FRIGGIN' WAY IN THIS LIFETIME, BUDDY!" So I have a 1's and 0's idea for Bluetooth/smartphone implementation: How about an application that locks out the ECU unless you punch in a code on your smartphone? That would be a feature offered nowhere else in the collector car universe, and I think it would be pretty easy to program! And if you choose to let your teenage son drive the car to the prom, you can assign him a special access code that will start the car and run it in a low-performance mode. (You could have different performance modes for different drivers, that would come up automatically.) The only possible downside would be if you aren't able to use your smartphone for some reason. If the battery is dead, then you could plug it in to the cig outlet to boot it. But if you've lost it, or it's been stolen, then you're out of luck, unless there's some "code" entry button for input directly to the ECU. It could be a one-button input, and you would simply push the thing multiple times, like pulse dialing on an old telephone. Anyway, I think that would be the ultimate defeat mechanism. NOBODY could run the engine without the code (or without replacing the ECU).

I haven't a clue where it was filmed, but the first car seen in a 2010 movie ("5 Star Day" on Netflix), driving down a lonely street at night at approx. 2:00 into the movie, was an S30 Z. The interesting thing was that it had absolutely no significance to the movie. It just happened to be there. (The kid's car, which appeared later, was a Porsche 914.) What are the odds of a 70's era S30 Z casually buzzing through the opening scenes of a 2010 movie, barely recognizable, apart from its sugar scoop headlights and the unmistakable reflections off its contour? :-) If you have Netflix, you might enjoy checking out this quirk of happenstance. However, the rest of the movie, about astrology and fate, is quite dumb, albeit somewhat entertaining. I felt generous, so I gave it 4 stars.

Nice color scheme! The black details really set off the orange!

Lenny: "one for the teenage son borrow the car for prom." Rev limited to about 3500 RPM, right? I'm wondering how difficult it would be to modify the distributor to serve as a cam angle sensor. It would take a bit of cobbling, but I'm thinking something like this: 1. Disable all advance mechanisms, probably by immobilizing the breaker plate. 2. Machine a new distributor cap without the plug wire connects. I think Chas (EuroDat) could either give you some great advice regarding plastic molding, or he might make the parts for you. (He made a very nice inspection light dome for me.) 3. Build into this cap a "rotor sensor." It would be an LED/photodiode pair between which the "blade" electrode of a stock rotor would pass. This sensor would identify the #1 position, and the reluctor output would give you your timing information. 4. Program a "set timing" mode into your firmware that would fix the advance to 10 deg BTDC, relative to the reluctor signal. Using this mode, the distributor could be turned as needed to achieve an actual 10 deg BTDC. 5. Ignition advance is then set by the Hellfire, and ignition is achieved through either lost spark or coil-on-plug. With this setup, sequential fuel injection would also be relatively easy. Note: the cap would have to be installed/removed when the rotor is turned away from the #1 position. I like Pharaoh's idea of an adapter on the AFM plug to break out connections for the Hellfire. However, my own preferred solution would be to have an accessory connector on the Hellfire that would run to a tiny breakout box under the hood. And in truth, I'd just make my own accessory harness to run from the Hellfire's accessory connector, straight to the under-hood accessory items.

Outstanding! My Z and I are getting very excited!