P4 ECM #1227748 questions

[Nick McAlpin]

A few (hopefully basic!) ECM programming questions.  

My questions will be pertaining to how the ECM handles the IAC 
stepper motor and the hot idle engine RPM and how it's set.  

I own an 88 4cyl Fiero 5spd.  I have not verified that the stock ECM 
is in it but it should be a P4 1227748 according to online 
references.  The engine is completely stock spec, including the 
195 thermostat.  Car is running fine, passes california smog, no 
check engine light, etc.  

Observation: The ECM programming has the annoying habit of not 
setting the hot idle unless the car is at a complete stop.  I can 
start the car up totally cold, and it high-idles (~2000rpm) as 
expected.  I can then drive for an hour on the highway (i get directly 
onto the highway without ever coming to a complete stop after 
starting the engine).  when i finally come off the highway an hour 
later and come to a complete stop, the ECM still is "stuck" at high 
idle ~2000 rpm.  If I sit at a complete stop, the ECM will step down 
the idle in fairly noticable ~100rpm steps until it reaches 1000rpm.  
If I don't wait the full time for it to come down to 1000 rpm (say I 
start driving again when it's at 1500), the next full stop the engine 
will come back to 1500, and then step down to 1000 from there.  
Either way, once it gets to 1000rpm it holds that just fine and idles 
fine for the remainder of the drive and is just great.

Question 1.  Is it appropriate for the ECM to act this way?

Question 2.  Should I try a different prom?  apparently there are at 
least two PROM's that are appropriate for this ECM/engine/tranny.  
Or are the different proms likely just calibrated for different tire 
sizes, and likely to be identical in actual function.

Question 3.  (uneducated suspicion) could the ECM be losing the 
hot idle IAC steps setting between each time I drive the car, and 
has to find the proper idle each time?  Is it supposed to remember 
the proper steps for the IAC to achieve hot idle?  For all I know the 
ECM could be losing everything between each startup.  How can I 
check this?

Question 4. Should I contact GM and see if my prom is an old 
revision/version, where there might be an updated/better version to 
try that might behave better?

Question 5. If i'm off base, will someone please point me in the 
right direction?

thanks!!!!!!!!

nick
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