Date: Mon, 9 Feb 2009 16:56:59 -0800
Reply-To: Scott Daniel - Turbovans <scottdaniel@TURBOVANS.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Scott Daniel - Turbovans <scottdaniel@TURBOVANS.COM>
Subject: Re: Bucking, hesitation between 1500 and 2500 RPM when hot
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some of my thoughts.......
you might be getting a slew of emails suggesting your temp sensor
........Temp Sensor II ........the one at the thermostat housing.......it's
a critical input to the ECU.
throttle switches are often off........you should at least check that.
Pretty easy to do.
on your oxygen sensor comments.....
the green wire goes to the ecu, and is the input to the ecu.
it's shielded.......and that shield connects to the ECU.........and to a
ground wire there........that goes back to the engine block.
The body of the oxygen sensor is grounded to the exhaust system
...........as shown by current track 25.
you should be looking at page 97.89.
looking at my 86 I see the brown ground wire disappears into the main
harness and it's not easy to tell where it grounds.
you could just unplug the connector plug and use an ohmmeter to check
continuity and resistance to ground.
if it tests OK that way, it probably is all right.
you could also just add your own ground for that wire if you needed to.
the white wire is power, for oxygen sensor heat, from the main relay.
that wire should have power on it any time the key is on I think.........and
certainly any time the engine running.
oxygen sensor heat is not absolutely critical to making the engine run, or
run right. Of course you want that system working.......
but not likely that lack of oxygen sensor heat is keeping your van from
running properly.
I do read of, from time to time, a shorted out oxygen signal in the oxygen
sensor sometimes, but have never seen that myself......and sort of 'don't
believe in it.'
oh.....in general..........you should just undo, clean, and tighten all the
Ground Wires by the coil, on the left side of the engine compartment, and on
the engine block, left side, especially that one - I see them quite corroded
all the time. I recommend a general WD-40 spray down , moderately, of any
engine that's showing signs of corrosion. Just don't spray it inside the
alternator......but everywhere else is good.
that many new parts makes me nervous.
a part being new is not an automatic guarantee that it's good........or that
it was installed correctly either.
I don't know who installed your new engine .......
but I commonly find a few workmanship errors on waterboxer engine
installations. You'd think anything related this way would do it from the
beginning though.
Scott
www.turbovans.com
----- Original Message -----
From: "Jerry" <jbvelo@BELLSOUTH.NET>
To: <vanagon@GERRY.VANAGON.COM>
Sent: Monday, February 09, 2009 3:49 PM
Subject: Bucking, hesitation between 1500 and 2500 RPM when hot
>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