[Gmecm] IAC control??

[Darryl M Gilbert]

Hello: Hmmm. It is best to make sure all your sensors are indeed working
ok. Not sure about 88 Pontiac, but my 85 El Camino has a sensor for the
gauge , and another for the ECM (1227747) The 1227747 does jack idle if
the battery voltage is low trying to bring the voltage up to specs. If
the Alt is not generating proper output it will increase idle. It also
checks coolant temp, (this is a choke function) if sensor is bad or poor
connections it will effect the idle by possibly thinking engine is cold,
or possibly to hot. Make sure map is working properly and adjusted
properly. Pull temp sender and attach an ohmmeter. Put in a pan of water
with a thermometer and watch its resistance as the temp rises. You can
heat water to 212 at sea level, so that should be enough. Do you have any
way of reading the ECM, like a laptop?? If you have a laptop for
practically nothing you can have a nice do-dad to see what your ECM sees.
If you need more info let someone know
Darryl   dgilbert78 at juno.com
On Thu, 9 Jun 2005 17:41:54 -0700 (PDT) Cowen <captain_krill at yahoo.com>
writes:
> Hello! I'm trying to trouble shoot a 1988 Pontiac 2.8l
> with a '727.  Problem is, the IAC retracts the pintle
> for starting, and then (intermittently) doesn't extend
> again.  Then the car idles at 2000 RPM. This car is
> not pulling any codes - I checked a few times, and I
> just get a reassuring "12". 
>   If I put the ECM into diagnostic mode, the pintle
> extends just fine, every time (so the IAC seems to be
> OK).  If I extend the pintle, leave the IAC
> disconnected, then start the car, and finally
> reconnect the IAC with the car running, it runs
> perfectly.  It even compensates for power steering
> load.  
> Question is, what inputs does the ECM need to set
> idle?  Coolant temperature, power steering pressure,
> and what else?  
> Other notes:  the battery is crap, does the '727
> increase idle speed when Bat Voltage is low? Also, the
> temperature GUAGE works fine, but the temp indicator
> light is always on.  If the ECM uses the same
> (faulty?) sender as the indicator light, shouldn't it
> pull a code?
> Thanks for any suggestions!
> 
> 
> 
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