Engine/Power - EJ25T (STI and 2006+ WRX) Discussions about the USDM 2006+ WRX and WRX STi 2.5 liter turbo flat-four.

06 WRX negative fuel trims @ low load & rpm

Old 07-26-2018, 10:05 AM
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Location: San Francisco Bay Area
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Car Info: USDM 2006 WRX Wagon
06 WRX negative fuel trims @ low load & rpm

Hi all,

I have a 2006 WRX wagon with 160k miles, currently on Cobb Stage 1+EBCS ACN91oct. Having some slightly concerning readings for AF Learning.

At idle, my AF Learning 1 has dropped down as low as -8.25%, which is further than the +/- 5-8% that Cobb deems is healthy. I don't believe it's a tuning related issue since I've been on the Stage 1 tune for about 2,000 miles now without issue.

While cruising around 2500 RPM, AF Learning 1 is around -5%. When I give more than 30% throttle, AF Learning 1 is between -2.74% and 0%.

The only positive fuel trim I've seen was +0.78% on rare occasions when letting off the throttle.

AF Learning A = -8%
AF Learning B = -5.5%
AF Learning C = -4%
AF Learning D = 0 (I believe Cobb did this intentionally, as the car would be in open loop at this point)

Used seafoam through BPV vacuum line, and cleaned the MAF about 1,000 miles ago. I'm reaching target boost (~14psi) just fine.

I've emailed Cobb as well. Anyone have advice on this?
Bill Peralta is offline  
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