[T3] '72 FI won't idle down

[Keith Park]

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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