Secondary throttle plate sticks closed, feels like a detent. How to fix?

[pentiumbased]

Hi all, I posted about this lasted month on bimmerforums for my US E36 318i, but got no responses. I thought I'd have better luck in a forum more dedicated to the m42, especially since (to my knowledge) only the m42/44 has this style of throttle body, and since E30 owners seem to be more enthusiastic about this engine in general.
I think the throttle body is different on the E30, but mechanically it should be the same as the one on the E36, going off of pictures online.
Below is copy pasted from that old thread:

The secondary throttle (the bigger one) on my 94 318i is hard to open when it's fully closed. It feels like a strong detent in the middle of accelerator pedel travel. It takes mild to quite heavy pedal pressure to unstick it. Sometimes it's very stuck and other times it barely sticks. When it's very stuck, my fingers are not strong enough to move it manually in the engine bay. It will stick again every time it is closed. The primary is fine all the time, and after the secondary is unstuck, it feels normal until it's closed again.
It makes throttle control for any acceleration beyond "leisurely" quite difficult.

I'd like to ask those who have looked closely at the dual-stage throttle body of the M42/44 for some insight on how to fix this. That way I'll have less chance of breaking it when I take it out to mess with it.
I will also take this chance to ask if the throttle cable is ever worth replacing. Mine feels alright, but I've been spoiled by DBW so I don't know what a good cable throttle is supposed to feel like.

Thank you

[roguetoaster]

Start with disconnecting the cable(s) at the TB. Then move the TB by hand, which will tell you if it's cable or TB.

If cable, replace, and they do go bad.

If the TB, it's not really serviceable, so I'd opt for a used unit. If you still have the TB preheaters in place (can't recall if E36s have them anyway) it makes removing the throttle assy difficult, but achievable. If you end up removing it from the car, be careful with those hoses.

The service you can do on your TB if required is just clean/lube it. Mostly at the plates (remove the intake boot to inspect), and at the return spring assy.

[pentiumbased]

Start with disconnecting the cable(s) at the TB. Then move the TB by hand, which will tell you if it's cable or TB.

If cable, replace, and they do go bad.

If the TB, it's not really serviceable, so I'd opt for a used unit. If you still have the TB preheaters in place (can't recall if E36s have them anyway) it makes removing the throttle assy difficult, but achievable. If you end up removing it from the car, be careful with those hoses.

The service you can do on your TB if required is just clean/lube it. Mostly at the plates (remove the intake boot to inspect), and at the return spring assy.

The cable does not move with the linkages if the linkage is moved by hand. It feels and sounds like metal-on-metal stiction breaking loose.
When I had the intake boot off to look inside today, the timbre of the sound changed to a more reverb-ey and metallic one, suggesting that the sticking point is coming from inside the TB.
I think the secondary butterfly plate is sticking against the bore. I applied Vaseline to the lower inner edge of the butterfly, which helped temporarily, but it might have been a fluke.
Is the butterfly hitting the bore the way it's meant to rest/stop? I didn't see any lip on the bore where it could rest, but I wasn't looking very closely because I didn't have the boot all the way off.
Is there a way to make the secondary sit ever so slightly more open like you can with the stop screw on the primary linkage?

[roguetoaster]

Take the throttle cable off, inspect and operate just the throttle by hand while looking at the butterflies.

Most likely, the bushing that the throttle shaft rides in is worn out. That's accelerated by a bad cable or lack of free movement in the progressive linkage.