Sorry to waste bandwith, but the message below was returned, so I'm posting
here, assuming Darrell will read it.

Date: Wed, 16 Apr 1997 20:00:36 -0700 (PDT)
>From: Tom Young <young@sherlock.SIMS.Berkeley.EDU>
To: Darrell Boehler <dboehler@nyx.net>
Subject: Re: '86 idle revisited and other comments (fwd)
In-Reply-To: <199704170025.TAA22658@cdale3.midwest.net>
Message-Id: <Pine.OSF.3.91.970416194556.1348A-100000@sherlock.SIMS.Berkeley.EDU>
Mime-Version: 1.0
Content-Type: TEXT/PLAIN; charset=US-ASCII

On Wed, 16 Apr 1997, Darrell Boehler wrote:

> Tom ,this info is just great.This procedure worked  like a champ on my 78
> westy.It has much the same wheel and spring as you mention on your vanagon.
> I rigged a heated exhaust gas oxygen sensor or hego that I had replaced and
> kept that was just laying around  from a non vw.Sticking it in the exhaust
> pipe I found it read .2 volts at idle and at 3k rpm 0v.As I tightened the
> spring the meter started reading higher and 5 notches the meter read .5
> volts at 3k just like you said it should.I now read .7 at idle and the idle
> rpm slowed down some,after bringing the idle back up to 900 rpm with the
> air bypass screw all seems fine and I went for a road test and let me tell
> you my westy has never run better,even seem to have more power and just
> wants to run. 

Darrell:

I'm glad it worked for you, but the readings you report just don't make
sense.

A very rich mixture should read HIGH, and a lean mixture LOW.  For 
example, before I adjusted my air flow meter, the ohm meter read over .9 
volts no matter where I set the adjustment screw.  As I tightened the 
spring the readings started dropping; I stopped when it started 
fluctuating around .5 volts.  (By the way, I understand that's what 
you're really looking for... a rapid fluctuation above and below .5 volts.)

The readings should be taken BEFORE the catalytic converter, if you have 
one, so readings taken "up the tailpipe" don't really work.  Also, I 
understand (but don't really know) that any use of an O2 meter should be 
taken in an AIRTIGHT port early in the exhaust.  Oxygen coming in up the
tailpipe can give false readings.

It sounds like you got some improvement (the seat of your pants tells you 
so) but I think the readings you report are suspect.  I have read 
somewhere (I don't remember where) about a procedure setting the idle air 
mixture "by ear" so to speak (i.e., no reliance on CO meter) so if you 
can find that (maybe the Haynes manual?) you might recheck it at some point.

PS.  In thinking about this some more, I understand the O2 meter 
generates a voltage based on the differential between the O2 in the 
exhaust and the O2 in the surrounding air, so I'm not sure what a heated 
O2 sensor stuck up the tailpipe is really monitoring.  
 
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Tom Young               young@sherlock.SIMS.Berkeley.EDU
Lafayette, CA  94549    '81 Vanagon
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