[W126 Coupe] HIGH IDLE

[Jim]

Hi all
     Its a 84 500sec euro
Problem
          After normal warm up idle " 900rpm" the idle moves to 650rpm at 13 deg temp and is then normal for 10 minutes or ten hours , or whatever it happenes to feel like that day.
  Non  of the fixes in the Archives or the fix on the main board by Serge seem to match my problem..
  Its either 650 or 1500 nothing between except during warm up When its 900
With the  Idle Control Unit   REMOVED from the fuse box I can recreate the 1500 high by removing the 2 pin connector from the idle air valve. when off its 1500 and 650 when pushed back on???   But!! if the idle is 1500 before i remove the plug its 1500 on or of?? With the OVR and fuse removed nothing changes.
Oh, forgot to mention . With the Control unit removed  I jump the pins that power the fuel pump.
  Strange, with the control unit removed It can be 650 or 1500 ?? does that suggest its (control unit) ok?
Have not removed the idle air valve. Is this straight foward or are there problems?
Question
        Engine is at normal idle (650) for ten minutes or hours. What would then command it to rev at 1500. Even with the idle control unit removed??
James
Down Under
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