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Old 11-28-2020, 02:58 PM   #1
TurboQueef
Scooby Specialist
 
Member#: 86700
Join Date: May 2005
Location: Otsego, MI
Vehicle:
2005 STI
FP Red:[email protected]

Default 2017 STi fuel trim issue

I build and tune my own (and kids) cars.. this issue relates to my sons 2017 STi

So... 8 months ago installed ID1050's and Cobb AF intake. Adjusted the shelf stage 3 map (MAF) due to not installing fuel pump, reg and rails. Had no issues until a month ago when suddenly the fuel trims (both short and long term) started adding fuel like crazy in the 2400~3200 RPM range at low to light load. The trim add total is 35~40%

To date I have taken these actions:
-Pressure test intake system (no leaks)
-Replaced MAF
-Replaced O2
-Checked fuel pressure (was OK)
-Leak down (was OK)
-Re scaled intake (worked fine for a day then AFU again)
-Switched tune over to speed density (no change)
-Disabled fuel trim correction (yea, it went lean, bucked and was just plain pissed off).. Update here.. I ran this test again and data logged "Roughness" and Cyl 3 showed a value of 2 and just before letting off, cyl 1 showed a value of 1. 22% throttle, -2.33 vac, AFR was 18/1

Any ideas?

Thanks

Jeff
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Last edited by TurboQueef; 11-29-2020 at 11:58 AM. Reason: add more detail on tests
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