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Throttle Stop setting procedure

 
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Smoothie  



Joined: 01 Jan 2003
Posts: 8029
Location: DE (the one near MD, PA, NJ)

PostPosted: Thu Feb 14, 2008 7:01 am    Post subject: Throttle Stop setting procedure Reply with quote

It's set at the factory, does not normally require adjustment, bla bla..
1) back off the adjusting screw until there is clearance between its' tip and the throttle valve lever
2) place a thin piece of paper between the screw tip and throttle lever
3) turn the screw in until it lightly contacts the paper (basically using the paper as a feeler gauge)
4) from this position, remove the paper and turn the screw in an additional 1/2 turn

Showing a series 2 931 TB, it's the small screw just below center in this pic -

(The real idle adjustment "idle bypass screw" for the S2 931 can be seen at the bottom, 1/3 from the left, within the vertically-oriented boss.)

Once the throttle stop is set, leave it alone (as it should have been from the factory). Any idle speed adjustments are done with the idle air bypass screw.
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Rasta Monsta  



Joined: 12 Jul 2006
Posts: 11356
Location: PacNW

PostPosted: Sat May 24, 2008 2:48 am    Post subject: Reply with quote

Hey Smooth, I was out looking at Shag's S2 TB and realized the thick spring around the shaft was pulling against the return spring, so if the return spring let go, you would get WOT. . .so I reversed it.

But I see yours is this way as well. Is this the proper setup?
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Fasteddie313  



Joined: 29 Sep 2013
Posts: 1561
Location: MI

PostPosted: Fri Jul 10, 2015 12:22 pm    Post subject: Reply with quote

931 S1 TB...

So I had my TB off today, welded the TPS plate back up so all 3 bolts are usable, adjusted TPS switches, etc.. My smaller butterfly throttle stop vibrated out some time ago and I replaced it today..

I find that the vacuum port nipple on the side of the TB, the little brass one that supposed to be for post TB vacuum afaik goes through and actually lands on the charge tube side of the butterfly when closed VS landing on the intake side as my logic says it should..

So I adjusted the small butterfly so that its cracked just beyond that vacuum port so the port would actually see post TB vacuum..

That didn't work out so well, with the idle air screw 2.25 turns out from bottom that gave me about 2k RPM idle, seating the idle air screw all the way down only brought me down to about 1700 rpm...

So I went back and adjusted the butterfly stop to where it just brings the butterfly off the walls and it stops on the screw.. Giving me a good idle adjusted with the air screw but leaving the "post TB vacuum port" on the wrong side of the butterfly, not good unless I'm overlooking something..

Whats going on here? Is that little port off the side of the TB not a true "post TB" vacuum port? because it sure isn't "post TB" its definitely PRE TB but only by a millimeter.

If that is the case that "vacuum" port is not going to work well with my BOV vacuum signal now is it....

Am I doing something wrong here? No I don't have any vacuum leaks, No my TB throttle plate axle bushings aren't whomped out, I think everything is right I'm just confused about that port being on the wrong side of the butterfly plate..

What gives? Is my TB that whomped out from not having a butterfly stop for a while to where it stops that far off from where it should and stopping it with the stop on the other side of that port is really giving me that high of an idle?

Do I need a new TB? Does anyone have a known good TB to look at and see where that little port lands in relation to the butterfly plate?

I ruined my TB running it without a butterfly stop didn't I? I think I answered my own question... It's always something..
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leadfoot  



Joined: 11 Dec 2002
Posts: 2222
Location: gOLD cOAST Australia

PostPosted: Fri Jul 10, 2015 5:18 pm    Post subject: Reply with quote

in regards to the side port, according to the vac diagram it's connected to the WUR and decel vavle off a tee, so would be boost for the wur and was under the impression the decel valve was vac...??? but could be boost only??
maybe stick a gauge on it and see what it references if youre unsure where it pops out inside...
should be fairly easy to drill and tap the TB for a new post throttle plate hose connection and run the bov from that, looks like there's enough meat on it...
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Fasteddie313  



Joined: 29 Sep 2013
Posts: 1561
Location: MI

PostPosted: Fri Jul 10, 2015 6:38 pm    Post subject: Reply with quote






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leadfoot  



Joined: 11 Dec 2002
Posts: 2222
Location: gOLD cOAST Australia

PostPosted: Sat Jul 11, 2015 9:32 am    Post subject: Reply with quote

dammit, just realized you have an 80 not an 81, sorry...
you should be vac then at the distributor and purge valve...

so yeah, the way you have it drawn in the last pic should be correct... I suppose the only thing I'd put out there is to watch out for cheaper silicon hoses collapsing under vac,

Not sure of the nipple size but you could always drill this out and install a bigger hose connection.

I'm a big proponent of nylon hoses....
Stu
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Fasteddie313  



Joined: 29 Sep 2013
Posts: 1561
Location: MI

PostPosted: Sat Jul 11, 2015 1:00 pm    Post subject: Reply with quote

You had me scared for a minute that I had all my vac lines wrong, I replaced them all with fuel line (rubber with braided core) and brass Tee's..

I figured something out...

If I just let my butterfly close all the way to the walls it's past that port... BAD..

This is what I did..
I idled the engine with the butterfly stop screwed open a bit (high idle), turn the idle air screw all the way in, and then adjust the butterfly stop to where it gives me about 750 rpm idle and lock it with the nut, then used the idle air screw to bring me back just under 1k rpm idle..

After setting it this way I had my upper charge pipe off again to dink around with more stuff and I checked out where the butterfly was landing VS that port hole..

The port hole lands just under the barely open crescent of the butterfly, which I would think would give me post TB vacuum + possibly some venturi effect from air rushing through the tiny crescent so fast..

I think it will be just fine as a post TB vac port like this, I will test vacuum to this line off the TB as soon as I get my boost/vac gauge in the mail..

I do not plan to install my boost/vac gauge to this line but I can use the gauge to test vacuum at the line before I install it to the BIG old pop off valve line under the manifold, to make sure I'm getting VAC from this TB nipple as I think it is designed for..
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Fasteddie313  



Joined: 29 Sep 2013
Posts: 1561
Location: MI

PostPosted: Mon Jul 13, 2015 11:42 am    Post subject: Reply with quote

Did some testing..

Idle air screw all the way in, testing by tongue..
If I open the small butterfly with its new stop to about 1500 rpm idle I get great vacuum at the line I pulled off the BOV..
If I turn the idle down to just under 1k by way of butterfly stop the vacuum to the BOV line decreases substantially and pretty much disappears if I close the small butterfly any further, this should not be this way no?

Any reason I shouldn't seal the old vacuum port and re-drill its hole a little more toward the intake "post TB" side of the butterfly to solve this issue?
Is this what you mean by?
leadfoot wrote:
Not sure of the nipple size but you could always drill this out and install a bigger hose connection.


I'd just buy an Audi 5000 TB and replace it but I can't spend any more money right now even if it is only $30
The small things just add up too fast..

If this only affected my BOV I would just plug it in somewhere else but this also affects my distributor and purge valve.
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Fasteddie313  



Joined: 29 Sep 2013
Posts: 1561
Location: MI

PostPosted: Wed Jul 15, 2015 9:47 am    Post subject: Reply with quote

OK i'm starting to believe my red circuit is not supposed to be post TB vacuum like I thaught..

By the way this is explained there should not be vacuum to connection 1 (red circuit) and applying vacuum to connection 1 will give a racing idle just like I had when I tried it that way..






And therefore connection 2 (blue circuit) is the post TB vacuum circuit..

And this whole time I'm thinking my TB is worn out because my butterfly lands on the wrong side of the port for connection 1 (red circuit) but it looks like it is not supposed to land on the post TB side of the butterfly..

Ugh..
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