12 volts does not go to the throttle switch. That goes to the auxiliary
air regulator. Since you had the 12 volt connector to the throttle switch,
it is fried. Now, since the 12 volt connecter is going to the switch, I'll
assume the other connecter is going to the auxiliary air regulator. Since
the regulator is just heating coil, the ECU is seeing this as a switch
that is always closed. Closed at full and open throttle is the
expectation. So when you accelerate, the ECU thinks the throttle is closed
so at ~1,300 rpm you go into fuel cut off (Decel) while trying to
accelerate. Makes for a great ride. Then at some point you go into fooling
the ECU into en richened full throttle acceleration. Yes, it is confused.
Swap the connectors and replace the switch.

Dennis

-----Original Message-----
From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf Of
Martin Jagersand
Sent: Monday, April 23, 2007 1:31 PM
To: vanagon@GERRY.VANAGON.COM
Subject: Re: Jerks/surges when going from coasting to acceleration

Hi,

It's a gas, fuel injected engine. It's actually a re-import to Germany
from
the US.
I suspect it's a 1985, but could be '86 model. (German records show
re-import date,
not real year) VIN is WV2ZB0258FH068651

I finally identified the right connector for the throttle body switch.
Turns out I have the "combined switch" arrangement found in Bentley
on p. 24.35 and 24.58. (I had previoulsy been confused and probably
pulled the wrong connector when I didn't find the two usual switches on
top of the throttle body)

Checked switch:
Switch always open.
Checked other end of connector: always 12V.
I used a high impedance DMM, so not sure what voltage would be
with an analog meter.

Bentley says voltage should be 5V. So I guess there is a risk that this
IO port on the computer is broken.

I had thought to try the "cut off test" by shorting the connector,
but then was afraid I might break something more.

More precisely the jerking/surging symptom that started the investigation
manifests itself as:
1. when slowly poressing the accelerator from idle for a little while
nothing
happens, then it surges.
2. When coasting with little engine power the bus can get into some kind
of oscillation behaviour. It surges forward, then retards, surges etc.

Martin

On 4/22/07, Kenneth Lewis <kdlewis@northstate.net> wrote:
>
> You weren't quite clear, is it a diesel you are having problems with? If
> not
> I would tackle the three throttle body adjustments. Especially the idle
> position sensor.
> Ken Lewis
> http://neksiwel.20m.com/
> Vanagon mods, tech info and O2 sensor help
>
>

--
Martin Jagersand
University of Alberta
http://www.cs.ualberta.ca/~jag/