4ks idle : settings and ECU function

[roger@mostro.sps.mot.com (Roger Albert)]

Hi all,

So, my intermittent motor bog on my dear 86 4ks took a drastic turn for
the worse Saturday night.  The beast just went horribly lean (happened to 
have my 02 meter in the glovebox).  I tinkered a bit and eventually got
it limped home, though it was running really, really poorly, essentially
only >=3krpm, by the time I hit the driveway.  Looks like I'd temporarily
compensated for the lean condition and then it went away, leaving me with
horribly fouled plugs, and, no real idea of where my mixture or idle air
screws are in relation to where they ought to be.  Can't get it to run
well enough to even do the basic setup/adjust routine.  So, is there a good
basic position to return everything to as a starting point.  On carbs, you
typically go something like "mixure all the way in and then back out 3/4 turn"
 - or -  Idle screw adjusted till it just lifts from stop, and then in 1 turn.

Ideas?  This would be easy for the idle air screw (anyone know how far out
theirs is from all the way in?)  but harder for the mixture.  Short of dis
assembly and then counting threads, is there a way, say full in or full out,
and then x turns out or in from there?  -or- would the screw just fall out
it I backed it out too far?  

I'd be thrilled for any help.  I've really screwed this up but good.  ARghh!

Oh yeah,  so I've noticed that I can get it to sort of run (idles too high
and still virtually undriveable, but at least does idle) by disconnecting
the idle switch.  The switch, its adjustment, and voltage supply are all fine.
I'm not theorizing the switch is bad, but rather that the absence of the
"throttle-closed" signal just happens to help.  So, in that spirit, does
anyone know what the ECU attempts to do, based on that signal.  Enrich?
Lean-out?  Raise-idle?   Knowing that might well give me more info as to
which way I need to go on the mixture.  Note: the thing surges and hunts
so badly that the O2 meter is of no use.  The motor _does_ appear to be
attempting to control, thus the surging.

Thanks again for any tips on either initial settings, or knowledge as to
what the ECU does with the idle switch position info.

regards
roger

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Roger Albert (go Illini!)  Motorola.  Austin, Texas 
roger@mostro.sps.mot.com   Wireless/DSP Div.  56xxx
Red 94 Ducati M900 Monster  and  White 65 BMW R60/2 
Blue 1976 BMW R90/6 and  1974 R90/6 Sidecar project
1973 Moto Guzzi Eldorado, restoration now underway!
1986 Audi 4000S -- Yup, sometimes you need 4 wheels
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Opinions expressed are always mine --, never Moto's
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