PCM Diagnostics & Tuning HP Tuners | Holley | Diablo

when do stit's take over coming to a stop?

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Old Apr 5, 2006 | 12:01 AM
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Default when do stit's take over coming to a stop?

At what point do the stit's become active and start trying to keep the rpm at idle speed when rolling to a stop? Is it when you get under your throttle cracker disable speed?
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Old Apr 5, 2006 | 04:15 AM
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These are all stock settings:

I believe it occurs when the TPS is <= 0%, RPM <= 1200, ECT > 80* C, Engine speed is in error by more than 60 RPM for more than 1.3 seconds.
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Old Apr 5, 2006 | 06:33 AM
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Just to be clear, i'm talking about the IAC reacting to get rpms back to idle rpm, i'm not talking about the conditions for ltit to learn. So you're saying it doesn't matter if the car is still moving at 10 mph?
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Old Apr 5, 2006 | 07:56 PM
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The IAC starts working at 0% throttle position. Doesn't matter if you are rolling at 50 mph. Think about it, if not, the car would die once you let off the gas (unless you have a really big hole in the butterfly or you have the screw turned in and the throttle is cracked open at 0%).
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Old Apr 5, 2006 | 08:27 PM
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Mine doesn't seem to be working that way. It'll let the rpms drop below idle when i'm still rolling and the iac doesn't even react. I don't see how the iac can be adjusting to get back to idle rpm while the throttle cracker is messing with the airflow values.
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Old Apr 5, 2006 | 08:36 PM
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Originally Posted by 98Z28CobraKiller
The IAC starts working at 0% throttle position. Doesn't matter if you are rolling at 50 mph. Think about it, if not, the car would die once you let off the gas (unless you have a really big hole in the butterfly or you have the screw turned in and the throttle is cracked open at 0%).
Negatory ghost rider... IAC starts working before you start the engine, and continues until you shut her down.

P-Mack - I had a very similar problem. I had to adjust the follower decay rate to make a nice gentle transistion back to idle. If your car is rolling at 10 mph, the cracker may still have an effect on the IAC. Stock settings on the cracker are to deactivate around 1 or 2 mph. I believe both cracker and follower must be deactive or fully decayed before the PCM will transition back to an idle state.
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Old Apr 5, 2006 | 08:38 PM
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One more note, I found it helps to monitor the IAC stuff in the chart/trend displays. Makes a much better visual for what may be an influence.
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Old Apr 5, 2006 | 08:38 PM
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Originally Posted by TAQuickness
I believe both cracker and follower must be deactive or fully decayed before the PCM will transition back to an idle state.
Hmm, that's the info i'm looking for. Can anyone else back this up?
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Old Apr 5, 2006 | 10:38 PM
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I just went out and did some scanning. Looks like throttle position doesn't have to be 0% for the stit's to adjust. And from what I can tell, speed must be <= throttle cracker disable speed for the stit's to move.
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Old Apr 6, 2006 | 04:42 AM
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I can confirm the STIT is not restricted to standing short term idle trim.
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