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Re: [T3] 72 square, rough idle, #1 missing?


>From: "Jim Adney" <jadney@vwtype3.org>

>Okay, then you no longer have the 72 setup and you don't have a vac retard 
>at all. The single hose is a vac advance. You should time your
>car as if it were a 73. You will never measure any vacuum in that hose
>while your car is standing still; it only gets vacuum when up to speed >and 


>The vac advance line used to connect thru a valve next to the pressure
>sensor (on the left of the engine.) This allowed vac adv only in 4th gear. 
>In order for this to work the valve still has to work, the >switch on the 
>tranny has to work, and all the wiring in between also has to still be 
>there and connected up right...<cut>

Well it sounds like I have some sort of cobbled together thing then, or 
something inbetween years perhaps? (and possibly unique to california)

>There should be NO Tee. I strongly recommend that you
>just connect this vacuum line straight from the dist to the intake air

That I can do, this will elimiate the small line that goes to the 
deceleration valve though. I have been thinking about the function of this 
device, which unfortunately isnt described in detail in the manual. The 
decel valve would supply air into the air distribution manifold, either 
under vacuum or without. The large ports on this valve connect from the air 
cleaner through the valve then to the air disribution manifold, AFTER the 
butterfly (if I remember correctly) Since this was only installed on 
california models, (extra pollution controls) I will surmise that this thing 
is there to lean out the mixture even more while decelerating only. But 
since the vacuum source is connected to the small port just in front of the 
butterfly, then it would only see a vacuum when the butterfly is open. So 
that would mean that with no vacuum on this deceleration valve (and hence no 
vacuum on the vac adv the way its currently connected) you get a lean, 
unadvanced mixture when the butterfly is closed? So only while pulling a 
vacuum on this port, you get some vac adv and a tiny bit richer mixture (by 
virtue of a little less air being drawn into the air box). Does that sound 

>I've never been able to see much difference with the crossed wires. I think 
>it may make a small difference at idle with a cold engine.<cut>

I think you are probably correct

> > > (.027-.028") on the SPs?
> >
> >I am glad you mentioned this....the bently manual states .024 as >does a 
>haynes manual. The owners manual states .028 why the
> >difference?

Well I did take a look at the spark through a plug with it set to .024 and 
it was a nice blue spark. Perhaps I misread something in the bently manual 
and .024 was for a different year? At any rate I will likely re-gap them to 
.028 just to see if there is any appreciable difference.

>Note my comment in another message about the loose injector wires. This is 
>a common problem because it appears that Bosch changed the
>thickness of..<cut>

Yes I did read that article, and already have checked that issue. I have 
tightened them up some, but they are still too loose for my satisfaction. 
What I need to do is really ensure that the male ends on the injectors are 
clean, and take the female pins out of the connectors to clean/crimp them as 

>It sounds like you are electronically adept...<cut>

Electronics Technician/Engineer (more of a hands on electrical engineer, 
than a sit down at a CAD station all day type :)

Thanks for the info

Drake Lawson
San Jose, Ca.

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