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What ignition system are you using? The ECU uses the coil voltage pulse to trigger injection. Maybe the problem is actually in the ignition module. The coincidence with the tapping on the ECU might be imaginary. No offense, the human brain can rationalize itself in to knots. I had thought of this earlier - if the problem is repeatable and you can make it happen while you're in gear and moving, the tachometer should still show RPM if it's the ECU crapping out. If it's spark related the tach will drop like a rock.

Haha. Indeed. This is me, all day every day. No matter which way this goes, I will be using at least one of my ECUs as a learning/traning tool to do a refurb from the ground-up and truly learn every last function, and to really play with tuning. This is why I already had: A spare ECU, a spare AFM, the FSM, the FI Bible, Bosch Fuel Injection & Engine Management, an Ignition 1-2-3 distributor, and an oscilloscope...as well as a host of articles and posts from around the Internet. But I had planned to do this on my own schedule. It seems my Z has other ideas... In related news, last night I discovered that rebuilt ECUs are actually a dime a dozen; I just failed to Internet properly. I've fallen into some sort of pavlovian response mechanism where I assume everything is unobtainium and start scouring ebay and specialty z-parts shops. But if you look at AutoZone, O'Reilly, RockAuto, NapaAuto, etc. a rebuilt unit can be had for as little as $200, or $175 if you are willing to return a core. I've now re-added the standard parts-jobbers for future needs. It looks like they still have some bits and bobs. If it is useless I can return it no problem, so I figured: why not? When it gets here I'll do some compare-and-contrast. More news at six. Film at eleven.

I have an embarrassment of riches when it comes to standard A11 600 000 ECU’s for 280’s. Can’t ever see using them all locally, so anyone interested in picking up a “Few” in the USA where you can distribute them from there to those that need? Asking $50 each. Ask me for volume discounts….. There are a few ZX turbo, both 280 and 300 if that suites your fancy. I can try to build a list. Similar situation with AFM’s…..

Sometimes I take a best guess, no matter what the depth of my knowledge on a subject, and just try something. Then hope my brain will take the results and come up with something better. In retrospect, I doubt that the transistor(s) was/were the cause of the problem. I imagine that almost any open circuit or short inside the ECU could cause it to malfunction. Your situation is unusual in that it seems so repeatable that it's almost controllable and is the same for two different ECU's. Maybe you're just losing a connection at one of the pins. Probably one of the multi-vibrator functions! 🥴

Wow. I wish I could nap a set of pistons/seals/springs/washers for $85. If you see another one of those, please send me a quick note to let me know? Nobody will see the pistons after they are installed, so it's not like you're going to be judged on whether that coating exists or not. And I understand about polishing it off... The decision which is better...Keep some of the original failed coating, or just remove it all. Totally understand. If you do decide to look into it, there is probably nothing very special about that coating, It's a black oxide coating on steel. It's a controlled rusting kind of coating. Similar to "gun blue". Any coating shop should be able to reproduce it, but cost prohibitive for a single piece. As for the changeover point between the stamped lettering and the cast-in lettering? In that other thread it appears that point is between 7/70 and 12/70 when they changed the markings from stamped-in to cast-in. I got the chance to mess with a 9/70 car and it had the cast in lettering. So with a sample size of one, I could narrow the date window down to between 7/70 and 9/70. However: 1) It's a sample size of one. 2) I don't know if it was the original brake master on the 9/70 car, and... 3) The 9/70 car was an automatic, and some of the stuff on the autos is different than the manuals from the same month (valve cover for example). All that said, I think your MAY car should have the stamped lettering.

The large cans bolted to the outside of the chassis.... Labeled NEC D411A... Those are discrete transistors, but are a unique pair in the design. Those are the final output transistors that drive the injectors. There are only two of them, and they are known as "Darlington Transistors" because of the internal construction. The discrete transistors I was talking about are the much smaller black plastic bodied things with three legs. I whipped this up labeling some of the components: And you had asked about the copper tower and blue things near the connector... The copper towers are coils (aka inductors or chokes) and the blue Chicklet things are capacitors. Those two components in conjunction act as a filter on the incoming signals to the ECU in an attempt to eliminate high frequency noise. They originally designed the ECU with provisions to put those filters on many of the signals going to/from the main connector, but it appears they decided somewhere along the way that they are not all necessary. So they only populated a couple of them by the time they got to the end of the run. Most of them are just shorted across with a piece of wire. Hope that helps.

Roo, Nice work on the brake stuff. I have a couple comments / questions about the master cylinder: First, where did you find the rubber seals you used to rebuild the master? Second, the pistons originally had a black oxide coating presumably for friction reduction and/or corrosion protection. It looks like you hit the pistons with a wire wheel and burnished that coating off? Any thoughts about having them recoated? And last, a little pedantic, but I'm thinking that is not quite the correct master cylinder for a 5/70 car. I'm no expert on the early cars, but I think you should have the one with the ground and stamped "F" and "R", not the cast-in markings. The correct one I believe would look like this: There was some discussion about such matters here >> https://www.classiczcars.com/forums/topic/65579-brake-master-cylinder-46010-e4602-up-to-91971/?&page=3

I've used common jackstands for years. )n the 280ZX in both front and rear there are obvious places which can support jackstands. In the rear, I slide a floor jack under the differential, lift on it and place jackstands under the places in front of the axle where the suspension bolts to the underbody. it's not hard to find stout places that can support the stands. What the factory manual says aren't the only places you can support the car if you're thoughtful about it. In front on my 280ZX, I slide the floor jack under the cross beam beneath the engine, then position the jackstands under the stoutest place in the frame rails with a chunk of 2x4 on top of each jackstand to spread the weight out. On my 280ZX I jack up the front first, then the back. It's low enough that getting much of an angle on either end makes it hard to access the other end. you may have to slide the jack in from the side, not the front or back. Lift carefully. Push on the car and make sure it's stable. Push on it after the jackstands are in place, and double-confirm that it's stable. Patience and thought will yield a safe result.