Date:         Mon, 9 Feb 2009 16:14:01 -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
Comments: To: Jerry <jbvelo@BELLSOUTH.NET>
In-Reply-To:  <C5B61D26.3EB%jbvelo@bellsouth.net>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed

The true O2 sensor circuit ground point is nowhere near the O2 sensor
and does not share any wires with the O2 sensor wiring. That brown wire
to the #12 ground point is only for the HEATER part of the O2 sensor had
has nothing to do with the true O2 circuit of the ECU.

The small bundle of wires that goes to the connector on the side of the
distributor has a brown wire branching off from it that goes to a nut or
bolt on the engine block, usually near the distributor. That single
brown wire from that bundle is the critical O2 sensor ground.

Mark


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
>
>
>