Motronic 4.1 newbie-continued

[Derek Kaznoski]

Thanks for the responses so far.

I was able to get the car to idle by changing the position of the flapper 
reference along the potentiometer, effectively increasing the resistance for 
any given air flow.  This was a bit of a rough idle with near-stalling upon 
initial throttle opening.  I noticed that at this "pseudo-idle" the flapper 
was completely closed.  Manually opening the flapper just a bit by moving 
the potentiometer arm smoothed out the idle and improved the throttle 
response.  This was still the case after putting the flapper reference on 
the potentiometer back to original setting. Squeezing off the air bypass 
hose to the idle speed actuator had no effect on the "pseudo-idle."

>From this, I assume that the idle speed actuator is not letting air in (if 
it were, the flapper should be a little open at idle, shouldn't it?).  Thus, 
manually opening the flapper allowed in a little air, effectively 
"substituting" for the idle speed actuator.

I took off the ISA and examined it. The valve seemed to open and close 
without difficulty.  I went ahead and cleaned it with throttle body cleaner 
to be sure (thanks Dylan).  I noticed that in the fully closed position, 
there was about a 3mm gap present, i.e., the valve is over-rotated past the 
closed position.  I couldn't adjust this because the adjustment screw was 
frozen.  I suspect that because of this maladjustment the valve doesn't 
completely open like it's supposed to (i.e., it's about 3mm less open than 
it should be at any given time).  I reconnected the ISA and cranked the 
engine while watching it.  It seems to function.  I still think, however, 
that it isn't letting air through because of the above reasons.  I'm 
planning to replace it.  If anyone thinks this is a bad idea, please let me 
know.  Any other input is greatly appreciated.

Again, sorry for the long-windedness.

-Derek Kaznoski
'90 Alfa Romeo Spider

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