The symptoms you describe may be a sign your basic settings are just a tad
off. With the switch working as you come down to idle you are momentarily
going into fuel cut off and then when fuel is back on the O2 sensor is
ignored and a slightly over rich mixture and/or over advanced timing is
giving you the slightly high idle until the mixture leans out again. With
the switch disconnected there is no fuel cut off and thus no O2 sensor
bypass. Also, if the idle is staying near 900 RPM the controller is not
fully in control. 750-850 is the spec although I do like to set it at the
high side. Note that on the 1.9 the fuel cut off goes as early as 1,100 rpm
and this scenario is what causes those engines to go into the idle surge or
hunt mode.

Dennis

-----Original Message-----
From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf Of
David Beierl
Sent: Thursday, October 16, 2014 6:11 PM
To: vanagon@GERRY.VANAGON.COM
Subject: Re: Weird "idle" problem

At 05:57 PM 10/16/2014, Dennis Haynes wrote:
>Closed throttle if the engine
>is being overrun such as coasting or slowing in gear at some speed the
>injectors will actually get turned off until the engine drops down to
>some lower point. This seems to be about 1,300 rpm on the 2.1.

This doesn't change anything about your procedure, but on the 2.1l the
closed-throttle switch does affect idle via the much more intelligent idle
speed controller vs the 1.9l.  On my '89 if the idle switch is working the
warm engine idles down to ?1200? - I forget exactly - for a couple seconds,
then drops to 900+ and stays there.  If the switch isn't working, it has a
slightly unsteady idle a bit above 1,000 rpm.  I've never tested a different
idle speed controller, but even if this is not correct behavior of my idle
controller it still shows that the controller is cognizant of the throttle
switch.

Yours,
David