Date: Mon, 9 Feb 2009 19:23:26 -0800
Reply-To: mdrillock <mdrillock@COX.NET>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: mdrillock <mdrillock@COX.NET>
Subject: Re: Bucking, hesitation between 1500 and 2500 RPM when hot
In-Reply-To: <C5B64683.404%jbvelo@bellsouth.net>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
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
>>>
>>>
>>>
>>>
>
>
>
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