John, if you had read my last message all the way, you would know that
the problem you are experiencing is with the oxygen sensor circuit.  It
could be the ground for the oxygen sensor.  Follow the wiring to the
hall sensor on the distributor and back track it about 5 inches.  You
will find a brown wire coming out of the harness and it should be
grounding somewhere usually on the driver's side head.  If that ground
is there and fine then I would say that your wiring from the ECU plug to
the oxygen sensor plug (green wire) is bad.  This is a coaxial wire and
over time the insulation between the inner signal wire and the outer
shield wiring breaks down until you have periods where the oxygen sensor
signal is corrupted.  So no matter if you have a new oxygen sensor, or
not, no matter if the oxygen sensor is actually hooked up or not, the
ECU is seeing a bad signal.  Check this wiring with an ohm meter,
however because it is an intermittent problem, some times you will not
get anything.

--
Thanks,
Ken Wilford
John 3:16
www.vanagain.com
Phone: 856-327-4936
Fax: 856-327-2242

On 12/28/2010 1:51 AM, John Rodgers wrote:
>  The current O2 sensor is a fairly new one, official VW type with
> shield and factory cable and connector.
>
> I think I need to get the 'ol test meter out and check connections and
> grounds.
>
> John
>
> John Rodgers
> Clayartist and Moldmaker
> 88'GL VW Bus Driver
> Chelsea, AL
> Http://www.moldhaus.com
>
>
> On 12/27/2010 5:20 PM, Dennis Haynes wrote:
>> The O2 sensor ground reference is through the brown wire in the hall
>> sensor (distributor) harness .
>>
>> Dennis
>>
>> Sent from my Windows Phone
>>
>> -----Original Message-----
>> From: Evan Mac Donald
>> Sent: Monday, December 27, 2010 4:34 PM
>> To: vanagon@GERRY.VANAGON.COM
>> Subject: Re: Progressive rough running - until ignition reset
>>
>>
>>
>>> There is a ground that isn't. It ismost likely at the ECU.
>>>
>>>
>>>
>>>
>>> ________________________________
>>> From: John Rodgers<inua@CHARTER.NET>
>>> To: vanagon@GERRY.VANAGON.COM
>>> Sent: Mon, December 27, 2010 3:46:25 PM
>>> Subject: Progressive rough running - until ignition reset
>>>
>>> Volks,
>>>
>>> I have a general Vanagon troubleshooting question - today driving home
>>> from an enjoyable Christmas gathering with all my family,  the van
>>> engine started twitching - a little skip at first, then as the miles
>>> rolled it got worse and worse. I was sweating getting home in all that
>>> snow and rain and raw weather we were having, and sure as heck didn't
>>> want to stall out and spend time on the side of the road in that
>>> weather. I managed to make it off I-65 at the southern exit onto Shelby
>>> Co 25 on towards Columbiana. By the time I got to the last hill just
>>> outside town - I was down to about 10 miles an hour, and coasted down
>>> that hill into town to the main stoplight. The plan was to go through
>>> the light on green, and pull over in a BigBox store parking lot. Didn't
>>> get the chance. Light changed, and the engine stalled. I turned off the
>>> wipers, the heater fans, and the head lights, shut off the ignition,
>>> and
>>> then hit the switch again. She fired right up, purring like a
>>> kitten. No
>>> more trouble......... until well up the road. Same thing over again.
>>> Just a little twitchy at first, then got progressively rough. This
>>> time,
>>> while coasting, I turned the switch off, and back on. The engine
>>> cleared
>>> it throat, and purred like a kitten. Did it twice more before I got
>>> home.
>>>
>>> So - what could be happening that turning the ignition off and back on,
>>> results in temporary clearing the problems. At first I thought fuel,
>>> then some king of ignition trouble, then an electrical fault for sure.
>>> Electronics somehow.
>>>
>>> Any ideas??
>>>
>>> Thanks,
>>>
>>> John
>>>
>>> --
>>> John Rodgers
>>> Clayartist and Moldmaker
>>> 88'GL VW Bus Driver
>>> Chelsea, AL
>>> Http://www.moldhaus.com
>>>
>>
>

--
Thanks,
Ken Wilford
John 3:16
www.vanagain.com
Phone: 856-327-4936
Fax: 856-327-2242