[T3] Irregular Idle....again...

[Jim Adney]

On 9 Nov 2012 at 14:57, J. Jonik wrote:

> A while back, the 71 (73 engine) (Std FI) had idling problems 
> 
> Now I have a 73 engine (thrust bearing in 72 case was shot) that runs and sounds great. Made two long round trips to Connecticut (from Philly) with heavy weight aboard on return trips.   Nothing like test-runs on G. Washington Bridge.

Did you swap in ALL the '73 components, including the brain and 
pressure sensor?

> Not even a hint of a problem....EXCEPT a little oddness a couple of
> times.  Turned out that the distributor mounting stud was loose...so
> distributor had a little play  

That's an odd stud to come loose; I've never seen that happen. Hope 
you fixed it with some Locktite.

>   But, now (coincidental with that stud job?) the idle is kind of like
> someone's sending Morse Code messages with little pushes on the
> throttle.   No backfires.  It's a frequent, regular up and down, not
> slowly up then down.  When revved just a bit, or a lot, no
> irregularity is evident.  Engine sounds great otherwise, and starts
> very easily. 

This may be normal, or it MIGHT be that the throttle valve switch 
(TVS) is misadjusted. I have a FAQ on how to adjust this correctly, 
as the Bentley gets it wrong.  

How much variation are you seeing? If it's only 50 rpm or so, that's 
pretty normal with a cold engine and may get better once warm. Keep 
in mind that this is a 43 year old design. Idle stabilization wasn't 
as good then.

> -Changed Pressure Regulator, twice, with good spares.  No difference to speak of.   A little, but hard to tell.
> - Cleaned spark plugs.
> - Cleaned and messed with distributor...different points, different condenser, different
> distributor body itself, and different trigger contacts.   Vacuum adv. passes the suction test      No difference noted.
> - Hose from AAR to Air Distributor was loose.  Ah Ha!   Trimmed both ratty ends a little and re-installed tightly.   No difference noted re/ idle..
> - Put hose clamps on those fat manifold hose sections.  Maybe a percent better, but not a fix.

Most of these sound like shots in the dark, and I REALLY dislike the 
hose clamps on the fat manifold hose sections. Those need to be able 
to slide a bit as the temp changes and they are totally unnecessary 
if the engine is assembled properly. (But re-assembled engines are 
often not done correctly!)

If this engine has ever been apart, you might want to check the 
gaskets between the intake runners and the heads. They should be 
~3/16" thick plastic, not the thin steel ones that were used on 
beetles.

> Have not, yet, removed and cleaned, or changed, the AAR....but screws
> and nuts are tight.    Still can't find info on how to adjust that
> little set screw inside. 

I've never had to re-adjust one. The only problem that happens with 
the AARs is that they get stuck. They either work or they don't.

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