Welp. Tore it all down and put it all back together and no fucking luck. It's gotta be the IACV!? I would really, really, hate to buy one, put it in and it not fix my issue though..
And the socket for the plug on the hardbody light only needs slight trimming to get it to plug in. Not exactly the same I guess, but it does work..
Edit: Ordered a new IACV. $135 from Nissan race shop. I hope this does it...
Edit 2: NO response from nissan race shop for my order, which I will probably cancel, maybe they're closed for COVID or something? But I've got an idea. the IACV is composed of a 2 devices, the AAC (Auxiliary air control) and the FICD (fast idle control device) I believe my problem is not with the AAC as I have been able to adjust the AAC duty % through the nismotronic and it seems to affect the idle. I think * maybe* the FICD is malfunctioning and I don't have AC so I don't need it anyway.. I plan to try to disconnect the FICD and keep the AAC connected, but the kicker is that both are connected to one plug, but I have an idea to jumper the pins for the AAC and leave the FICD disconnected or possibly de-pin the socket for the FICD.
I should note (and may have mentioned before) that when the fans are on loading the engine a little bit more the idle is better..
Wish I had found this before as I didn't take the IACV apart. I may have been able to test the solenoid operation for the FICD. Doh!
https://www.nicoclub.com/archives/z32-tech-curing-erratic-idle-issues-part-1.html
Edit 3:
Well, that didn't do anything.
1.) Tried running w/o the FICD valve and only the AAC Valve. I was able to get it to idle around 13.8-14.5 AFR except I had to set the Min. AAC duty to around 50% and adjust the screw on the IACV all the way in which would only lower the idle to 1100 rpm. No Thanks.
2.) Put 12V to the FICD pins and heard audible click and tried while idling and it significantly raised the idle. Seems to work fine.
3.) Died a little bit inside.
I'm running out of ideas..
Symptoms again:
When cold it will idle at 15-16AFR pulling approx. 19.3 in/hg albiet a little rough. Not violently shaking, just a little bumpy.
When warm it will idle at 11.8-12.5 pulling appox. 20.8 in/hg smooth as butter. but trying to lean it out to 13.5-14.5 it misses and pops.
Somewhere between cold and warm the vacuum jumps from 19.3 to 20.8 for no 'apparent' reason.
Pressure test intake?
Pressure test cooling system?
Check Compression?
Check/replace O2 sensor?
Check injectors for sticking/leaking?
Check timing?
Why does it pull less vacuum up to a certain point/ECT? Why/how would ECT affect vacuum?
But if it is pulling more vacuum, and an injector (brand new nismo 740s) was leaking/stuck, it might draw in more fuel, possibly not atomized, pulling raw fuel into the engine and causing it to miss fire.. ? IDK..
I did have a problem with a new RC injector on my RX7 that had something in it, causing it to dump fuel, it was bad though. But when I checked the fuel pressure, it didn't leak down really quick or anything.