Date: Sat, 18 Nov 2000 10:36:28 -0500
Reply-To: Joe Romas <jromas@COLUMBUS.RR.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Joe Romas <jromas@COLUMBUS.RR.COM>
Subject: Re: purpose of throttle valve adj.
Content-Type: text/plain; charset="iso-8859-1"
Jim,
The reason is to precisely control the amount of air at idle through
the idle bypass screw instead of the TV. The screw is more exact then the
butterfly plate. This is all to control the emissions at idle. My 84 van
seems to be missing the stop arm/screw or I don't understand how to adjust
it. My 84 has a screw that contacts the idle switch but nothing else that
would provide a good stop for the plate. It just goes until it kind of
binds.
Joe
----- Original Message -----
From: "James Creech" <jacreech@VISUALLINK.COM>
To: <vanagon@GERRY.VANAGON.COM>
Sent: Saturday, November 18, 2000 9:50 AM
Subject: purpose of throttle valve adj.
> Here is a question for those who've delved more deeply into the mysteries
of
> the throttle valve and how it serves the EFI system. In adjusting my gap
> setting this week to fall w/in specs (.002 - .004") and having a hard time
> with it before successs, I realized it would be very helpful to know
exactly
> why such a tiny gap is essential.
>
> Here's what I know from Bentley (24.58 and 24.62): At idle the TVS (the
> switch) should be fully closed, giving elec. continuity, thus telling the
> ECU: (a) correct idle injection quantity (b) to switch off inj. quantity
> during deceler. fuel shutoff (c) correct ignition point setting in idle
(DLS
> function [BTW, what is "DLS"?])
>
> My TVS was improperly adjusted, such that my switch was never closed at
idle
> at all - thus no info sent to ECU and very poor idle, esp. when cold. But
> WHY such a small gap? Is it to ensure when giving throttle from the
> acceler. pedal that the idle, info to ECU is cancelled, or no longer
given?
> Is there another reason? If that is the only reason, one would think the
> gap could be a little larger, for when giving more throttle the switch is
> still going to open very soon and give infinite elec. resistance, thus
> telling the ECU we are no longer in idle mode.
>
> I must be missing some key info here. Sorry I am so ignorant of the Bosch
> FI system - I have the book on order which should educate me for more
> intelligent questions in the future. For now, maybe there are others on
the
> List who could benefit from knowing how this TVS works.
>
> A final question: It appears the large spring encircling the TV shaft
does
> the work of returning the TV to closed when the accel. cable is released.
> But what does the skinny spring do? Is it for optional cruise control or
> something essential to those systems w/o CC? How should that skinny
spring
> operate when healthy? Mine seems to do nothing - does NOT pull the
smaller
> "arm" back at all - that smaller "arm" just stays put w/o free movement.
Is
> that a problem?
>
> Thanks very much,
> Jim Creech
> 87 Westy GL 2.1
>
| 
