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Old 04-17-2010, 09:15 PM   #1
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Default MS Parallel - does stock ECU need IAT?

I've been battling with a "changing tune" issue ever since i got my MS.. basically ambient temp affects my tune.. Colder = richer, hotter = leaner. I've played with easytherm, i've removed some resistors at braineack's suggestion, nothing seems to be working for me..

I see that the stock ECU is still getting a signal from my GM IAT.. does it need to? What, if anything, is it using that reading for? Even if it got the reading, would it be able to make any sense of it seeing as it's not the stock sensor?

Thanks,
Tomaj
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Old 04-17-2010, 10:17 PM   #2
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Well i cut the wire from the parallel harness to the stock ECU for the IAT sensor, and now i seem to get 0 ADC for the IAT gauge..
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Old 04-17-2010, 11:09 PM   #3
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Lots of us have parallel installs with the same wiring (before you cut it) and don't have major issues with the weather.

When the car is cold in the morning, do your IAT and CLT readings approximately agree with reality (a separate thermometer or the weather report)? The default GM IAT values have worked pretty well for my car. The stock CLT is a hair off but it hasn't caused any issues with the tune. Your problem sounds like it could be an easytherm or a heat soak issue. Where is the IAT sensor mounted?

Do you have any cooling system mods like a reroute where the heater core skips the mixing manifold, or maybe a gutted t-stat that would affect the car coming up to operating temperature in the winter?
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Old 04-18-2010, 07:14 PM   #4
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i put the wire back together and re-flashed using IAT bias of 2625... the sensor reads correct in MT at 61*F, verified using multimeter (w/thermometer..).

we'll see what happens...
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