Date:         Sat, 18 Nov 2000 09:50:52 -0500
Reply-To:     James Creech <jacreech@VISUALLINK.COM>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         James Creech <jacreech@VISUALLINK.COM>
Subject:      purpose of throttle valve adj.
Content-Type: text/plain; charset="iso-8859-1"

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