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Date:         Wed, 11 Feb 2009 17:41:30 -0600
Reply-To:     Jerry <jbvelo@BELLSOUTH.NET>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Jerry <jbvelo@BELLSOUTH.NET>
Subject:      Re: Bucking, hesitation between 1500 and 2500 RPM when hot
Comments: To: mdrillock <mdrillock@COX.NET>
Content-type: text/plain; charset="US-ASCII"

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 >>>> >>>> >>>> >>>> >> >> >>


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