Very Rich at startup & Bad Idle Speed Controller ?

[Michael, Dave]

I have been trying to trace a subtle problem with our 200QA (2 knock
sensor MC) -  On startup, the exhaust reeks of unburnt fuel. This is
especially true if the car is shut down hot, sits for ~1/2 hour and is
then restarted. 

As  part of my diagnostics efforts, I figured I would check the mixture
(CO). But to do that, one first needs to set/verify  the idle speed
controller current is 430mV. And that's where I am facing problems. I
followed the procedure in the Bentley, but can't get the ISV current to
change - its stays at 400mV no matter what I do with the idle speed
screw. The idle speed screw actually changes the idle speed (ie - the
ISV controller isn't controlling); I can go from 500 rpm to 1000 rpm and
the ISV current does not change. I ran all the checks at the ISV
controller connetcor pins, and all the terminals check out OK. So all
things being equal, it would seem that I need a ISV controller.  Only
bummer is that its over $200.00 and I hate to get one unless I can be
sure I need it.

In all other regards, the car runs like a freight train - it's just the
gas smell on startup that's a problem.

For the gas smell, other things I figure I need to check are:

1. Cold start valve not leaking
2. System and control pressures


Any ideas on the ISV or gas smell?

TIA!

Dave
90 200QA 201K
98 m3/4 75K
02 MCS 12K