'90 200tqs (MC) Cold start idle stability problem

[G. O'Malley]

I'm looking for advice on a cold idle stability
problem.

When I start my car after a long sit (say overnight,
all day) it won't idle for the first 30 seconds or so.

The car starts fine, cranks for only 2 seconds and
catches.  If I don't work the throttle, it will not
maintain RPM and stall......  I don't notice a miss,
it just won't maintain RPM.  If I work the gas, it
runs smooth.  

After 30 seconds or so (enough time for O2 sensor to
go closed loop; other?) the idle settles down and the
car runs great.
Runs great on warm start

The problem became visible when I replaced the
injectors, before that, I had to crank a long time to
get it to fire, and I may have ignored the problem.  I
really can't say....

I have reset the mixture since I replaced injectors.  
I adjusted the mixture with a scope, tweaked the
frequency valve to about 55% neg duty cycle.  This was
up from about 40% neg. duty cycle.  Little to no
effect is noted.  

I am at a bit of a loss on this cold idle problem. 
Overall (today, knock on wood) the car is running
great with the exception of this problem.... 

Recent engine related work includes.... Michelan man,
Fuel pump, Knock sensor #1, Lifters, 

any btdt's on this problem?
Thanks in advance,
Greg O'Malley
'90 200 tqs

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