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Sti Leaning Out during acceleration

Problem began again after we were cruising and under 4,000rpm low load no boost it jumped up to 18:1 stuttered for a second I left off then after that it would start to rise up acting like it wanted to lean out, it at times would rise up to 15:1 to 15.5:1

Parts are aem 340 pump Cobb 1050x injectors iag fuel rails and lines aeromotive fpr grimmspeed intake with box torque solutions turbo inlet

My fpr sits at 40-44 my intake temp was at 20-30, no signs of gas leaks anywhere, fuel pump duty was at 33% then 100% during wot before I started having this issue, I replaced front o2 sensor then the issue was fixed but came back, cleaned the maf, issue went away did a few pulls ran just fine didn’t lean out then it came back. Injector duty cycle was at 50% but I’m assuming it’s just because I’m on a stock turbo and stock tmic

What should I look for? Boost/Vacuum leak test, replace maf? Tune related?
 

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Just curious, what are you basing your ARF readings off of?

Yes, i would first establish that you dont have any air leaks. Try doing a boost leak test and vacuum leak test.

Ive never been a fan of cleaning MAF's, id always prefer to replace with new oem from Subaru.
 

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Just curious, what are you basing your ARF readings off of?

Yes, i would first establish that you dont have any air leaks. Try doing a boost leak test and vacuum leak test.

Ive never been a fan of cleaning MAF's, id always prefer to replace with new oem from Subaru.
Reading them from my AP as I don’t have a wideband yet.
 

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Yeah i wouldnt go by that. That AFR reading from the accessport is really only a short term fuel trim so to speak. You will see it make very quick adjustments. Even between shifts you may even see it go to 20:1 and also at times when off the accelerator pedal you will see it rise and climb. To accuratly get an AFR reading you will need a wideband set up.

I believe IWIRE makes an AEM wideband kit thats plug and play to use with the AP. It may be something to look into if you are going for a wideband.
 

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Yeah i wouldnt go by that. That AFR reading from the accessport is really only a short term fuel trim so to speak. You will see it make very quick adjustments. Even between shifts you may even see it go to 20:1 and also at times when off the accelerator pedal you will see it rise and climb. To accuratly get an AFR reading you will need a wideband set up.

I believe IWIRE makes an AEM wideband kit thats plug and play to use with the AP. It may be something to look into if you are going for a wideband.
100%

Though if you also felt it (vs just seeing it) then it could still be good info.
I'd smoke test it and get a wideband sensor to start.
 

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Is your fuel pressure 44psi at idle? Make sure the vacuum line is intact and connected to your FPR.
 

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Is your fuel pressure 44psi at idle? Make sure the vacuum line is intact and connected to your FPR.
Just tonight I check it was at 38 after I was done driving it and it’s been snowing so sometimes if I was sliding I’d slightly get on it I got two events one being -6.00 fbk and -4.50 fbk but no dam drop or FKL numbers came through so I’m assuming it’s just noise or it’s very possible I have a broken o ring in one of my injectors or it’s possible I have a vacuum leak, I did pull the tmic off today and there was an unbelievable amount of oil through the compressor side in the hose going to the y pipe oil through my bov and I have a iag v3 AOS which makes me come to think is my stock vf48 turbo going bad and is all that oil going into my intake bad as well maybe causing these issues?
 

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Just tonight I check it was at 38 after I was done driving it and it’s been snowing so sometimes if I was sliding I’d slightly get on it I got two events one being -6.00 fbk and -4.50 fbk but no dam drop or FKL numbers came through so I’m assuming it’s just noise or it’s very possible I have a broken o ring in one of my injectors or it’s possible I have a vacuum leak, I did pull the tmic off today and there was an unbelievable amount of oil through the compressor side in the hose going to the y pipe oil through my bov and I have a iag v3 AOS which makes me come to think is my stock vf48 turbo going bad and is all that oil going into my intake bad as well maybe causing these issues?
I think a vacuum leak will cause you to run rich under boost, not lean. How much oil did you see in your TMIC? Make sure the AOS and lines are not clogged or frozen.
 

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Just a slight bit to fill the palm of my hand, this is my fuel pressure at idle and it’s 14.5:1 to 14.7:1 at idle
That's probably a little more oil than normal, but I don't know if it's enough to indicate a failure. Fuel pressure and AFR are fine, what are your AF learning and correction at idle?
Have you duplicated the problem since?
 

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That's probably a little more oil than normal, but I don't know if it's enough to indicate a failure. Fuel pressure and AFR are fine, what are your AF learning and correction at idle?
Have you duplicated the problem since?
AF Learning 1 sits at 0 and AF Correction 1 sits at 0 to -3.12
 

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Discussion Starter #13
Those values are good. Try to duplicate it and get a log if it happens again.
I’ve hit boost in 3rd gear a few times today and from looking at my readings I’m hitting a solid 11.03 up to 6,000 rpm or so, so far it’s been good and not as much feedback knock as I usually get I’m still going to continue to look around for small things but a wideband is on the way
 
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