Thanks for responses concerning my "bucking and hesitation"
problem.  I worked on my Vanagon today with fresh ideas after
reading all suggestions provided.  Here is what I came up with:

The "Green" 02 sensor wire is shielded as you all have indicated.
My 02 sensor wire is clean, does not interfere with the shielded
section of the wire.  I tested the wire per the Bentley and those
continuity tests passed.

I also did all of the pin to pin tests as stated in the Bentley.
All continuity and voltage tests passed within specification listed
in the Bentley.  I do have a question concerning the continuity
test for:
Terminal #12 at the ECU end of the harness and terminal #87 at the
fuel pump relay.  I performed this continuity test and the result was
infinite resistance(open circuit).  I am confused about this circuit.  The
continuity test I performed is listed in the Digifant Pro Training Manual.
It is not listed in the Bentley.

http://www.obsolyte.com/vanagon/VanagonProTraining/DigiFant/040.jpg

According to the Pro Training Manual this tests the fuel injectors
and wiring.  This check is for total resistance which should be 3-5 ohms.

As I stated, my test indicated an open circuit between terminal #12
and terminal #87 of the fuel pump relay.  Is the Pro Training Manual
correct??
Could the Pro Training Manual be wrong??

I tested for continuity between terminal #12 and terminal #86 of the fuel
pump relay, the result was 4 ohms.

According to the Bentley wiring diagram page 97.106, the white wire from
terminal #87 at the fuel pump relay goes directly to the fuel pump. I
checked continuity from terminal #87 to the fuel pump connector.  This
reveled 000 ohms which according to the Bentley is correct.

I did not see a test in the Bentley for checking continuity between
terminal #12 and terminal #87 at the fuel pump relay.  I did check the
continuity of the injectors per the Bentley with the following results:
#1 INJ  16 ohms
#2      14 ohms
#3      14 ohms
#4      14 ohms

I also made sure my grounds were good.

Thanks for your help!!

On 2/9/09 9:23 PM, "mdrillock" <mdrillock@COX.NET> wrote:

> The shield is surely there. There is a smaller stranded wire in the
> center with green insulation. Then there is a stranded copper shield
> laid over that, and the whole thing is covered in another outer layer of
> green insulation. One thing that sometimes happens is someone replaces
> the spade connector on that wire without realizing it is coax wire. They
> strip off the outer insulation and think the copper shield wires are the
> conductor and crimp a spade on to the shield, likely shorting the shield
> strands to the center strands.
>
> The shield is part of the ECU harness and inside the ECU harness
> connector it is tied to a white wire going to an ECU pin to ground it.
>
> If you carefully slit the outer green cover near the end it will expose
> the shield. You might want to check with an ohm-meter to verify that the
> shield is not shorted to the center conductor, though it sounds like you
> may have already done so.
>
> Mark
>
> Jerry wrote:
>> Mike,
>> This is interesting information.
>> I have examined the green wire which goes
>> back to the ECU. The green wire on my
>> Vanagon does not have a braided shield
>> around the wire.
>> I have performed all of the pin to pin
>> continuity tests as per the Bentley for the
>> 02 circuit and all tests meet specification.
>>
>> What effect does not having a shielded green
>> signal wire have on the system??
>>
>>
>> Thanks
>>
>> JB
>>
>>
>> On 2/9/09 6:27 PM, "Mike Collum" <collum@myfairpoint.net> wrote:
>>
>>
>>> The "Green" wire in the 02 sensor circuit is the "Signal" wire and it
>>> resides within a shield.  The green wire and the shield must not short
>>> together.
>>>
>>> For the shield to work as a shield it must only be grounded at one end
>>> (the ECU end).  If it makes ground anywhere else it's no longer
>>> providing shielding.
>>>
>>> The wire from the 02 sensor itself, up to where it connects to the green
>>> wire, isn't shielded.
>>>
>>> Mike
>>>
>>>
>>>
>>> Jerry wrote:
>>>
>>>> I hope for some much needed advice on this problem.
>>>>
>>>> I have an 88GL which actually meets the electrical
>>>> specs of an 87 by looking at the Bentley wiring diagram.
>>>>
>>>> My problem is this:
>>>> When the engine is cold it seems to run fine.
>>>> At highway speeds all is well until the engine
>>>> reaches operating temperature.  After the engine
>>>> reaches operating temperature it begins bucking
>>>> during upshifts and throttle speed increase. When
>>>> I push on the throttle to increase speed there is
>>>> a significant hesitation.  The engine speed will
>>>> finally increase to meet the fuel demand and throttle
>>>> response. Engine speed above 2500 seems ok.  Throttle
>>>> increase above 2800 RPM seems normal(no hesitation).
>>>>
>>>> I am thinking this is an Oxygen Sensor GROUND problem
>>>> but am not sure.  I have read all the posts concerning
>>>> oxygen sensor grounds and I have questions.
>>>>
>>>> Where does the oxygen sensor ground(green wire)?
>>>> Does it go to ground at the #29 chassis ground by the ECU?
>>>>
>>>> I have a three wire oxygen sensor.  Where does the brown
>>>> wire ground from the oxygen sensor(chassis harness). The Bentley indicates
>>>> a ground at #12 ground in engine compartment(left). The brown wire
>>>> on my 2.1 02 sensor goes into the engine compartment harness which
>>>> runs along the front of the engine deck. I cant tell
>>>> that the brown wire goes to ground from the 02 sensor.
>>>>
>>>> I have cleaned and reinstalled all grounds, however
>>>> I combined some of the grounds at two locations on
>>>> the left engine firewall.
>>>>
>>>> I have a 2.1 Boston Engine installed in MAR 2008
>>>> New AFM
>>>> New Idle Control Unit
>>>> New 02 sensor
>>>> New Distributor and Hall sensor
>>>> New ECU
>>>> New Evaporative control canister
>>>>
>>>> This problem has got me down!
>>>> As you can tell I've replaced just about all components.
>>>> I also have the harness installed between the AFM
>>>> and original chassis harness.
>>>>
>>>> Thanks for any advice.
>>>>
>>>> JB 88 GL Guido
>>>> New spark plugs, cap, rotor and wires
>>>> New fuel injectors and fuel lines
>>>> New fuel pressure regulator
>>>>
>>>>
>>>>
>>>>
>>
>>
>>