[T3] '72 FI won't idle down

[jadney at vwtype3.org]

A flow restrictor will help, if the actual cause can't be found. There's an even 
smaller restriction in the IAD front cover.

I don't understand why the left breather port would pull oil out of the case; 
that's the uphill side!  

On 9 Jun 2026 at 22:46, Keith Park wrote:

> Im running a bit of a Bastard setup on the 2056, it´s a 71D based system
> with the 72 dual type can that the 914 2L's ran stock.  One thing I had to
> do was put a restriction in the line to the crankcase breather, something
> Ray Greenwood suggested, about 3mm, that seemed to work
> And allowed it to breath but kept idle within range.  I also had to plug the
> left side head breather to keep it from sucking the sump dry on long hard
> hill pulls, that may have been a result of the restrictor or not, but as I
> have it now things are happy.
> 
> Keith
> 
> 
> Topnotch Restorations
> topnotch at nycap.rr.com
> http://www.topnotchresto.com
> 71 Squareback  "Hothe"
> 65 Notchback  "El Baja Rojo"
> 93 RX7  "Redstur"
> 13 Subaru Outback "Blendin"
> 
> -----Original Message-----
> From: type3-vwtype3.org <type3-vwtype3.org-bounces at lists.vwtype3.org> On
> Behalf Of David
> Sent: Tuesday, June 9, 2026 10:34 PM
> To: type3 at vwtype3.org
> Subject: [T3] '72 FI won't idle down
> 
> It has been about 25k miles since I restored Elwood, and I have always had
> to restrict the IAD inlet to get it to idle down to 850rpm to set the
> timing. ( yup: '72 with dual diaphragm vacuum canister w/ ports plugged).
> After every tune-up spec is set: the resulting idle speed seems to be a
> little higher than the previous last year -  to where I can't bring it down
> to spec, so I live with it. As of today the idle is around 1300 and I've had
> enough, so I'm trying to get to the bottom of it. All my FI components are
> the correct '72 versions.
> 
>  
> 
> The idle screw is just an air bleeder screw, but it is ALL the way down to
> be shutoff. Vacuum canister is new, and it properly does the job of bringing
> the idle down about 80rpm at idle when plugged in. Fuel pressure @ 30.
> Plugging the warm aux air regulator results in only a minor drop of about
> 30rpm, so that's working. I have sprayed SO much carb cleaner around any &
> all intake gaskets & seals & injector areas that I must have the cleanest
> engine out there, but zero change in rpm to find any air leaks. I even made
> a bent carb cleaner nozzle hose to spray on the underside and backside of
> the IAD. Cold start valve has never been hooked up, but no rpm change when
> sprayed with carb cleaner. Rubber air intake tubes test good for no air
> leaks as well. I have the '72 decel valve installed & working, but plugging
> it for a test showed no issues. Readjusting the throttle switch made no idle
> difference. I substituted a known good spare pressure sensor, but made no
> difference at idle.
> 
>  
> 
> If it's a warm engine - and then I shut it off for say 30 minutes - it will
> start right up and idle correctly for about 20 or 30 seconds, and then it
> will increase itself back up to 1300 within 1 minute or so.
> 
> When warm - I can put my finger inside the throat of the IAD and totally
> plug the inlet "port" for the idle speed screw. This 100% plugging will
> result in a 850 or so idle speed (with the idle speed screw still all the
> way in and throttle plate still closed).
> 
>  
> 
> IIRC - the 2 FI heat sensors have very little to do with idle speed, but
> please correct me if I'm wrong about that.
> 
> I do have a backup brain I could substitute, but I'd like to hear any
> feedback before I go that route.
> 
> Sorry for the long post. I'm trying to give all info.
> 
> Dave Pallo
> 
> '72 Square ~ Elwood
> 
> Fairport, New York
> 
>  
> 
>  
> 
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-- 
*******************************
Jim Adney, jadney at vwtype3.org
Madison, Wisconsin, USA
*******************************