[T3] Irregular Idling...again...Update

[Jim Adney]

On 13 Nov 2012 at 12:41, J. Jonik wrote:

> Back to the Idling problems.
> 
>   Jim Adney asked if I have the 73 IAD and Breather, or if I kept the 72 IAD and Breather, when I switched engines.  I have what came with the 73. I only now saw how the two aren't the same. The 73 has an air hose going from the back of the IAD to the breather.
>   The 72, that I took out of the car, has no such hose. Breather is the same except its hose vents down.  (Mine always just vented into space but I THINK it was supposed to vent into the oil dipstick pipe.)

You need to have matching breather and IAD. That includes the 
functional hose if you use the '73 parts.

If you block off the hose and try to keep the '73 breather, you'll 
end up with no breather at all, which will end up pumping oil out 
around the rear end of the crank. Better to swap in the early 
breather.  

>   So....thinking that if that IAD-to-Breather hose is the only
> difference, I blocked off the hose to the IAD. Lug nut and hose clamp
> did the trick.  That helped cut the racing idle about in half, but the
> irregular idle is again noticeable.   And, still, the idle cannot be
> set. It's all the way screwed down. When I open it a bit, yes, it
> speeds up. 

Hmmm, that hose is supposed to pull some air thru the crankcase to 
ventilate it, as sort of PCV, positive crankcase ventilation. It 
shouldn't be able to pull in that much, because there's a small 
orifice in the cover of the IAD that limits the amount of air that 
can get in.

I wonder if running this "new" engine for a few weeks finally 
loosened up some dirt that was plugging that orifice.

'73s got timed differently, and it's possible that this kept the rpms 
down. Or maybe someone drilled out that orifice for some reason. (I 
think that's a REALLY long shot.)

> RE:  The AAR:  Is it a good idea to set AAR adjustment nearer to, or
> at, the plus sign? That direction cuts off the air flow.  Setting it
> at minus opens up the air. I did this thinking that I'm obviously
> getting too much air...more air, apparently, when cold engine warms
> up. 

Plug the AAR hose with your thumb. Does that slow the engine down a 
lot?

> I'm not yet clear on the idea of changing brain box and pressure
> sensor.  When doing the engine change, I left ALL the electronic
> things in the car. Nothing came with or from the 73...except engine
> block, breather, IAD, and manifold.  It all worked amazingly for about
> a month, doing some serious driving...until this idling mystery began. 

Have you rechecked the timing? Do you realize that the '73 timing 
marks are different? Which dis Have you checked that the mech advance 
is free? Something could have freed up, or gotten stuck in a 
different position.

Is this still the '71 distributor?

-- 
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Jim Adney, jadney at vwtype3.org
Madison, Wisconsin, USA
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