Open/closed loop Jeckyl/Hyde

[akallotte at juno.com]

Just started the motor and she's idling lean in open loop. 6E code in an
87 Vette, 24# SVOs at low to mid 40s PSI, 218/226 510/510 114 LSA cam,
idling at 700-800 in Park. The only code I've changed was inj constant
(25.9#), lower fan on, and higher tc lock. 

I went through the service manual idle set procedure today. Got
everything perfect. Shut it down, restart, idled at 1400, not the idle I
set.  In open loop, it runs poorly - lean, low vacuum, low idle, IAC wide
open. Once it hits closed loop, IAC closes completely, vacuum picks up,
good AFR, good idle.

What is causing this? I don't know if IAC or lean condition is causing
all the problems, although IAC would seem to cause the lean condition.
Why is the IAC wide open in open loop and closed in closed loop? I must
have to change something in my program, but what?  Commanded idle speed,
maybe?
 
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