PCM Diagnostics & Tuning HP Tuners | Holley | Diablo

Why are my STIT's staying at zero?

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Old Aug 20, 2010 | 01:48 PM
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Default Why are my STIT's staying at zero?

HPT Support says it's either mechanical or in the tune. Frost is helping me with the tune and it's the first time he's seen this.

I'm going to try scanning with the 2.22 release instead of the beta in case it's a scanner bug. If it's not that, how do I resolve this?
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Old Aug 20, 2010 | 02:23 PM
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What are your O2 sensors reading? What codes are set? What codes are turned off? If the PCM sees funky stuff going on with O2 oscillation, it will discontinue closed loop operation.
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Old Aug 20, 2010 | 03:38 PM
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Originally Posted by edcmat-l1
What are your O2 sensors reading? What codes are set? What codes are turned off? If the PCM sees funky stuff going on with O2 oscillation, it will discontinue closed loop operation.
They would update early on in the process and no DTC's have been changed since. The issue is STIT's, not STFT's. It's pretty strange!
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Old Aug 20, 2010 | 03:54 PM
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Originally Posted by Frost
They would update early on in the process and no DTC's have been changed since. The issue is STIT's, not STFT's. It's pretty strange!
OOPs! Misread.......

I had one one time that the STITs would lock in on the lowest base airflow number. Wouldn't reset to zero off idle. Never figured it out. Had to "tune around" it.
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Old Aug 20, 2010 | 04:15 PM
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There are some enable fields for adaptive idle RPM, like
off temperature. And if your TPS reads out of idle range
then it won't even try to trim. Any of this sound likely?

If IAC counts are moving around and RPM is being held,
I'd be thinking a PID screwup of some sort (what it thinks
is your STIT PID, returns zeroes). There seem to be some
occasional issues of that sort, though you'd think a '98
F-body ought to be a pretty known quantity. Then again
there's that (how many?) multiple-OSes deal....
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Old Aug 20, 2010 | 05:36 PM
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Try logging 24 bytes or less.
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Old Aug 20, 2010 | 07:05 PM
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I'll try that this weekend. My opinion is the software should notify the user if you're trying to log more than the supported number of bytes when you connect to the vehicle. I'm also curious how the software determines which bytes to ignore?
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