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Didn't know you were running a lumpy cam. That thread from zcar.com is interesting. A lot of what would be considered bad advice on how to get the 260 cam to run "right". Fiddle with the AFM, run direct vacuum advance, adjust the TVS so it's off-idle. wangsman's version of "runs great" seems to be pulling hard to 6000 RPM. Your issue is at idle. You can tell from the comments that some of the opinion might be more of an "I made it work" view. I'll bet their cars smelled like raw gas at idle. No offense to the two guys that said it can run just fine with the lumpy cam, but that's how the brain works. We probably all have memories of the guy in high school that thought his car was fantastic but nobody wanted to ride with him. @Jeff G 78 is one of the guys in the thread. He knows a bit about how to get these engines to "run right". It will be entertaining to see where you end up. How are you going to write a guide if you take it to a tuning shop? What goals will you set for the tuners? Today's tuners only know how to use computers to tune automotive computers (I just saw one of those car repair videos that the guy titled "millenial vs. carburetor" or something like that) . Take special note of the looks on their faces when they see what you're working with. Should be fun.

I had a similar problem 10 years ago in my race car. The +12V wire from the ignition was gone (a teammate inadvertently removed the wire while cleaning up the harness), so it wasn't charging. After a lot of head scratching before we figured out that several feet of the wire was missing from the middle of the harness, we ran a new wire from the ignition on to the alternator and it charged fine again. The wiring diagram (available online) will show you the color of the wire and the end connections. Do a continuity test from one end to the other and see if the wire itself is bad. Worst case, run a new wire.

Dan, I’ve completed the front Koni’s with Ebauch lowering springs. I’m very happy with the height and ride. I kept the stock insulators in the front. Next week will be the backs. I bought 240z insulators and will run Koni’s and Ebauch there also. I’ve finished my Differential refresh and just waiting for my Mustache Bar bushings and parts to get back from powder coating. I think the backs will be easier that the front because you can rock the whole assembly out from the car with taking the control arms off. Good luck! Sent from my iPhone using Tapatalk

So it really sounds like you've got weak / dirty connections in the EFI system, and that's not unusual at all. Very common situation for these cars. If you're going to take your car in for some tuning work, you need to be absolutely double dog sure that all your EFI connections are clean, solid, and reliable. Top priorities for me? If all of your connectors are still original (except for injector #1 which you have already replaced), I would go ahead and replace the other five injector connectors and polish up the pins on the injectors. I would also replace the temperature sensor connector with new, and polish the temp sensor pins. I would pull and polish up the dropping resistor connections. Lastly, I would inspect the AFM connector and polish up everything there too. Hope it's that simple!

So, I agree with you both that I think the mixture is off at certain RPMs, especially high RPM. However, the bucking at idle is completely new. I want to mention that my Z has the 260s cam, and I knew it was going to need a lot of tuning to get the original EFI to work right (adjusting the AFM flapper, timing, etc etc). Many people advised against it, but I believe with such a small cam most of it can be tuned out. However, I still think that something electrically or mechanically is amiss in my car, because cylinder number 5 now seems to have almost no change to idle or engine when at a little higher rpm. In addition, it is just running in general a lot worse than it used to before I started having these weird problems. Here is a what gave me faith with the stock EFI and the 260s cam. https://www.zcar.com/threads/biggest-cam-for-stock-efi.292280/ "I ran the Deltacams 260 cam with stock efi and it ran great. I ran the cam for a few years then sold the car since I had to many z's. Yes, 110.00 plus shipping. Don't forget the thicker lashpads to make up for the regrind. 0.160" thickness from courtesy nissan for another 36.00. this cam does require some tuning to the stock efi. Run more ignition timing, loosen up the afm flapper a few teeth, adjust the tps to the off idle position. You can run stock ignition timing if you move the vacuum advance to a manifold vacuum source. This will add vacuum advance at idle, so it will make the engine idle with 30 degrees of timing (10 initial + 20 vacuum advance). the cam has a very slight lope at idle. pulls hard to 6000 rpm. a nice improvement in my car. A 260 cam should idle in the 16 to 17inhg range. Lower than expected vacuum is a sign of low ignition timing and improper air/fuel ratio. A Z efi computer doesn't measure vacuum like a modern efi system, The only thing in a Z efi system that measures vacuum is the fuel pressure regulator" That being said, my vacuum is currently at around 15hg at 950rpm. So I either have a really bad AFR, vacuum leak, weird electrical issue, or it's that semi dead cylinder, or likely all of the above causing bad AFR. Thanks for mentioning the water temp sensor tweak, it is a great gadget. I made one many moons ago, and tried it to see if it would fix anything at high or low rpm following that comment. Didn't do much except bog the motor down with fuel, so I don't think the problem lies there. I am going to be taking it to a shop this weekend where they can actually measure my AFR, smoke test it, do real electrical work etc using all the big boy tools I don't have. As well as tune the EFI for the cam. I will update this forum once they find the issue(s), so to keep everyone informed. I would also like to mention if I get it running right with the 260s cam I will make a separate thread as a guide on how to tune the EFI for it, so members can use it as info in the future, knowing that putting a cam in the stock EFI is a highly debated topic. Thank you everyone for the help thus far! I genuinely would have zero headway when working on the Z without help from this forum:)

Some people have problems with Eibach springs. It seems to vary, almost like the springs are coming from different sources. The common problem is that the front ends up higher than the back. Others have no problems.

I'm going to guess that the jolt was a ball cage/retainer on one of the adapter plate bearings. People often find pieces of the retainer when they do a fluid change. The transmissions seem to just keep going though, it's amazing how destroyed they can look but still do just fine when new parts are installed. Draining the fluid will probably tell you something. Look for metal shavings and flat pieces of metal. https://www.researchgate.net/figure/Main-parts-of-ball-bearing_fig1_289540744

I haven't been super active in the forums, but I attend to the reported posts when I get a notice. We're pretty open here, so not sure yet how to filter spam. Maybe have to approve posts or something for a while, but that's more work for management. We'll see.

Hi Gavin , in this thread , SteveE saw my car then kindly provided his spare . He said he bought it with other parts from Nissan long time ago but never needed to used it . Kats

I made a video summarizing my install of the Silvermine Motors EPS on my 1973 240z. I'm impressed with the kit and 1st impression in the garage is that the system works really well. Just waiting for the salt to be washed off the roads before I pull out my 240z for the season. https://youtu.be/fF24zOops2M