Hello all, I am completely dry of ideas as I've tried many things on this forum, in the manuals, but I'm still not getting anywhere. The idle is fine for a second or two, then drops, or pops and sputters a little bit. Videos are attached.
For background info, it is an NA. No AC and no power steering. Pretty much all emissions equipment is removed - BAC, air pump, split air pipe, EGR, all that is gone. Otherwise I have a K&N cold air intake. Everything else is pretty much stock.

Things I've tried:
Adjusting TPS (1k ohms at idle and 5k at wot)
​​​​​​Adjusting idle air screw
Adjusting idle mixture (made it a bit smoother when I enriched it)
Checking for vac leaks
Cleaning the fuel injectors in ultrasonic bath
Trying another air flow meter
Trying without air filter
Trying another set of spark plugs
Checking compression (it's a newly rebuilt engine with about 500 miles on it)


And maybe some other things I don't remember. I'll take any suggestions at this point. Videos are attached. Thank you for your help!

 

its tough without the BAC/Emissions stuff, part of it is there to make the car run better.
couple things to check, the clutch switch. these cars, idle is a separate thing, and its turned on when the TPS is at zero, AND either the transmission in neutral, or in gear with the clutch in. if its not in the idle mode its going to do odd things

second you might try to raise the idle speed a little. the stock air injection puts air to the exhaust ports, and some of this goes into the engine. without the air pump, idle will drop because its essentially missing some idle air, so you could open the throttle a little.

and three, you might consider putting the BAC back on, its only purpose in life is to keep the idle speed at the spec

 

I think a few people now have suggested putting the BAC back on, which seems like it would require a few other components and I'll have to look into that. Thanks for your answer!

 

It never hurts to check/replace the temp sensor behind the alternator. .. . .It's cheap and relatively easy to change. . . It can certainly effect startup if it is out of calibration..

Also, cap the port going to the thermowax valve that supplies the double throttle diaphragm valve to take it out of line and ensure it is not leaking to atmosphere.

 

Hi all, accidentally posted this on a related post with a similar issue but I wanted to post here for closure. I reinstalled the bac valve - immediately fixed my idle. I had a few other issues like timing being off by several degrees, which helped, but then the idle air screw did not really help whatsoever after a certain point, would only raise it to 600 rpm. With the bac, it's now butter smooth! Lowered it to 750 rpm with the screw afterwards, and now it's perfect.