Thanks for the reply, that's correct, wired the CKP and CPS into the original factory CAS connector. I don't have the CAS anymore as I sold it with the 1.6 engine so can't try that, and I have checked every wire I could for anything loose including connectors at ECU. I'd be shocked if it was a loose wire with how consistent it is, and since I can drive around fine, as well as hold high rpms, just not accelerate hard at the high RPMs above 5k. Until 5k it's fine and also holding steady RPM around 5-6k is fine.

 

No good point I should have mentioned that so people can see it without opening up the tune.

I've been running 3ms dwell from the DIY basemap and I believe that matched trubokittys as well and is consistent with what I've seen people running. I tried 4 and 5ms as well but no improvement.

 

ignore

 

You make a good point, but is it impossible that there might a vibration at high rpm acceleration/engine movement which is causing the wire to become intermittent? I know it seems like using logic is best in these situations, but some problems
seem to defy logic. I would make a list of all the possible problems and then systematically replace each one to confirm that is not the problem. Of course doing that may yield nothing. I have had electronic intermittent issues which
have ended up being solved only by pure luck. (not Miata related) Good Luck!

 

Totally agree it's not impossible (and as a typical engineer that will over analyze, using my logic isn't always helpful haha) just can't find anything loose for the life of me so moving onto other possibilities at this point. Appreciate your input and I'll def update this whenever I eventually get to the bottom of it! Sequential spark COP conversion has always been on the list so I've got R8 coils and connectors coming to build a new ignition subharness, hopeful that will fix it so I can squeeze in one last track day before winter

 

Figured I'd wrap this thread up with somewhat of a conclusion. Ended up getting the R8 coils, built the sequential harness and ran the 2 new leads to the MS, all went very smoothly and car started right up and drove great. Retuned fuel a bit, spark felt nice and strong, ripped on it pretty hard on the street for 4 days no issues whatsoever until it started misfiring consistently again. Super frustrated, let the car sit for a few days, tested some stuff and did some thinking. At some point I had noticed my idle rpm has been changing (with no mechanical changes) and needed retuning throughout the season so that led me to finding that the IACV connection wasn't great. I could change the angle/wiggle/pull at the wires and the idle would change due to poor contact/voltage supply I assume. I unplugged it completely for a few days while waiting for a new one, and opened up the idle screw a bit to keep it running and didn't have any misfires. The OEM pins and seals had definitely seen better days at 30+ years old and saw some marks of heat, and after replacing them there's no more variation in contact/idle and I did not have any misfire since doing that a few days ago. Car is away for storage now but if anything changes next year I'll come back to this.

Only thing I don't understand is how a loose IACV wire could cause those sync losses/ severe misfires under load. My best guess is it would momentarily connect/disconnect and create noise in the ecu/electrical system. They do share the same white/red +12V wire so maybe it's possible. Maybe it is completely unrelated, I suppose I will find out next season haha. Thank you everybody for the feedback and suggestions!!