Who told you the ECU does not use the O2 sensor at idle? It definatley is.
Only if something is worng or the settings are so far out the system can not
compensate will it not maintain control.

Dennis

>From: Gregory Smith <gfs@SCATTERCREEK.COM>
>Reply-To: gfs@SCATTERCREEK.COM
>To: vanagon@GERRY.VANAGON.COM
>Subject: idle fuel calculations
>Date: Sun, 25 Nov 2007 13:50:03 -0800
>
>Another thing to keep in mind re: injectors or O2 sensor, the O2 sensor is
>not used by the ECU at idle.  This is why the CO adjustment on the AFM is
>used.
>
>So really the calculations using the volume are pretty close.  This would
>of course apply to a warmed up engine though, since a cold engine uses
>something like twice as much fuel.
>
>Years ago, I read an article about a test VW did in Holland (I think it
>was) where they fit some Golfs with Diesel engines that would
>automatically shut off at idle and automatically restart when needed.  The
>finding was that they were off about half the time.  This could save some
>emissions over time for sure.
>
>Ciao,
>Gregory Smith
>Olympia, WA
>'84 Vanagon