snitm

FYI, the skunk2 74mm TB is crap out of the box. Needs serious adjustment to avoid sticking throttle. Blipping the throttle resolves the stuck throttle but it is unacceptable and needs to be dealt with in order to keep the TB in the car.

Sideways

You need to set the stop screw or you will score the wall of the TB and the butterfly valve will stick.

Standard TB installation 101.

snitm

Huh, I'll try searching google for pointers on what the procedure is. But while the car was tuned today (at Evans Tuning in PA) there wasn't any noticeable throttle sticking on the dyno or during the street tune portion afterwards.

It wasn't until I got on the highway for ~30 minutes and then off real quick to drop a package off at UPS that I noticed the throttle sticking (requiring blipping the throttle to get it to stop). But over the course of the 4 hour trip home to MA the sticking got progressively worse. To the point that at the end it was actually quite uncontrollable and scary.

SO anyway, any further details on what I need to do with the set screw would be very much appreciated (is it the gold screw above the TB inlet in the pictures here?) FYI, not seeing any scoring of the TB walls...

edit: I think the screw you're referring to is the one with the nut on it that is below where the throttle cable connects to the TB. I can see that if I raised that screw up it'd hold the TB butterfly open slightly.. but won't that cause other issues?

snitm

Hmm, setting the stop screw is so basic that skunk2 completely glosses over the need to do it in their howto for their alpha TB?

Sideways

Set it so the butterfly is almost touching the wall but not quite. You get a little air past the butterfly but you need much more to idle thus the idle air valve lets the rest in.

snitm

But won't that primarily help with any sticking that might happen while the TB is completely closed?

My situation is that once the TB gets hot (happened as soon as only driving 30mi on the highway) once I need the TB to be closing more responsively it simply doesn't.. it gets stuck on close.

Or are you saying it applies to both open -> closed _and closed -> open?
So should I get the TB hot and _then_ take it off and adjust the stop screw while hot?

(I think the 2 different types of metal that skunk2 uses for their TB creates some of these problems.. the 2 different types of metal expand at different rates when heated)

snitm

I fixed my rampant stuck skunk2 TB problems.

Here is what I did:

1. took the throttle plate out of the TB (needed T15 torx to break staked bolts out)
2. beveled the edge of the throttle plate all around using a sanding bit in my drill
3. sanded the throttle plate all over using 1500 grit sand paper
4. polished the throttle plate and inside of the TB
5. reassembled the TB, used blue locktite on the throttle plate screws, and extended the throttle plate stop bolt slightly, reinstalled in car
6. had a vacuum leak due to too much air getting past the throttle plate
7. various experimenting with throttle cable position, stop bolt position, etc
8. finally arrived at completely removing the stop bolt for a perfect idle
9. added a washer behind each bolt of the throttle cable bracket to push throttle cable away from TB a bit
10. sprayed the throttle cable, throttle plate, TB spring with "One Shot" dry lube (had it from my ammo reloading setup)
11. SUCCESS!!!! (holy hell was that tedious and involved)

It was very fiddley to get this TB working well, and the tolerances on certain adjustments are tight so it could need maintenance to stay running perfectly over time.
E.g hopefully the throttle plate screws won't loosen -- but I'll check them peridiocly and re-torque as needed.

Couple related pics:

snitm

OK, but isn't the source of the idle air that the IACV is injecting coming from the 2 passages in the TB (the air is pulled along the intake manifold channel to the IACV) which you blocked?

I'll have to look again but I thought the IACV doesn't have any vacuum lines connected to it...

snitm

I plugged the 2 air passages in my TB, with my fingers, and the car stalled out. No idea how yours doesn't.