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Old 04-19-2013, 11:54 PM   #1
ccbremech
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Member#: 286915
Join Date: Jun 2011
Location: Victorville CA (SoCal)
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2004 STI
BLUE

Default Closed loop fuel target dropping to 13.xx AFR

Hey guys, my AFRs keep dropping to the 13's at cruise. I did some data logging and realized that my closed loop fueling target will randomly drop down to the 13's, sometimes even at idol. When it does drop, my AFR correction goes crazy and shoots up very high. Any idea why this is doing this? has any body else had this issue? Any idea how to fix it?
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Old 04-20-2013, 12:09 AM   #2
the suicidal eggroll
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Join Date: Jan 2004
Chapter/Region: RMIC
Location: Broomfield, CO
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2012 WRX

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On the 16-bit ECUs the rear O2 does nothing but check cat efficiency, on the 32-bit ECUs it also adjusts the CL fueling target. A bad rear O2 can drop the CL target to ~13.5 on the 32-bit ECUs, a pretty common problem when people remove the rear O2.

Last edited by the suicidal eggroll; 04-20-2013 at 12:15 AM.
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Old 04-20-2013, 12:47 AM   #3
ccbremech
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Ok, it's a 04 Sti so 32 bit ECU. Guess I will change it out and see if that helps. Thank you for your input! The car did run rich for a small amount of time so that may have caused it.
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Old 04-23-2013, 06:54 AM   #4
Bamofo
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TurboMike Tuned 2.35

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It uses coolant temp to add fueling. If your running hotter then it wants it will change the cl target for sure.
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Old 05-05-2013, 11:01 AM   #5
ccbremech
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Changed the rear 02 and I'm good to go now. Thx to all for your input!
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Old 05-09-2013, 07:26 AM   #6
Bamofo
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TurboMike Tuned 2.35

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If it happens again you can turn off that correction from the rear 02 with ecu flash. PM me your rom if you would like it changed. Glad you got it working!
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