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Old 10-05-2012, 12:01 PM   #1
MGBx88
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Join Date: Apr 2011
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08 WRX
OBP

Default System too Lean, running 50% boost

I did a good amount of searching, including the P0170 All you need to know thread.

I have been getting the CEL P0171 "System too lean" lately, and nothing mechanically has changed that I know of, except having my clutch/flywheel replaced.

My car has a AEM CAI, perrin dp, and AP cb exhaust, professionally tuned in 2010 for 18.5psi. It's currently maxing out just over 9.

When I give the car gas, I get the usual woooosh/pshh sound from the CAI, but there's a secondary sound that sounds like fluttering. There's also (what I think to be) a new sound from underneath the car, but I cannot find the source as my car is extremely low, and even when getting the front end up a small curb, I still couldn't get under.

I checked the MAF sensor, it looks clean, and checked what I could of the exhaust for leaks. I saw water drops where the mid-pipe connects to the y-pipe, could be issue?

Data Log...
https://docs.google.com/open?id=0B9M...TBnV3dFb0ZDNkU
not sharing at the moment,.... the original .csv seems to be working..
https://docs.google.com/open?id=0B9M...TBnV3dFb0ZDNkU
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Last edited by MGBx88; 10-05-2012 at 12:09 PM.
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Old 10-05-2012, 12:10 PM   #2
Source,LLC
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Location: Chicago,IL
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WRB

Default

if you are only hitting 9 pounds of boost you either have a problem with your EBCS or your wasteagate. Check to see that the wastegate arm isn't stuck open and that all the lines running from the solenoid are in good condition.
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Old 10-05-2012, 12:18 PM   #3
MGBx88
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Will do. Thanks for the reply.
Forgot to mention, there have been a few times where the car almost stalled at idle as well.
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Old 10-05-2012, 12:23 PM   #4
the suicidal eggroll
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2012 WRX

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You have a system too lean CEL? Did you reset the ECU recently? Because your AFL is 0, or right around there. I've never seen a car throw a system too lean CEL with an AFL of 0, it doesn't make sense. You need to add AFC to your logs as well, that's the rapid fueling correction in closed loop.
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Old 10-05-2012, 01:47 PM   #5
MGBx88
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Tightened the actuator as far as it will go, still only about 9psi. Parked the car and turned the wheel to take a closer look at the CAI, and the System too lean (bank 1) code reappeared.
Idle is still pretty rough, and there is a fluttery sound under the car. I'm thinking it's gotta be an exhaust leak. Once I get back in ill upload a sound/video file.
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Old 10-05-2012, 01:48 PM   #6
MGBx88
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To answer egg roll, yeah, I reset it whenever it comes up. I'll see if I can log that file for you
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Old 10-05-2012, 01:51 PM   #7
the suicidal eggroll
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Stop resetting your ECU...

The system is running lean, the ECU is telling you this. When you reset the ECU, you're making it run EVEN LEANER. You're also wiping out ALL evidence of the problem, so that nobody can do a thing to help you.

http://forums.nasioc.com/forums/show....php?t=2229323


That said - if the car runs fine after a reset, and gets steadily worse up to a system too lean CEL, AND you hear an exhaust leak under the car, this could be one of the rare circumstances in which resetting the ECU is not a horrible move. You probably have a pre-O2 exhaust leak which is feeding fresh air into your exhaust system, causing the O2 to read lean, and causing the ECU to dump in fuel to "correct" for the problem. Your gas mileage has probably gone to **** as well. You need to find/fix that leap ASAP or you could end up washing out your cylinders.

Last edited by the suicidal eggroll; 10-05-2012 at 01:57 PM.
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Old 10-05-2012, 02:32 PM   #8
MGBx88
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And I want to become a Auto Mechanic... tsk tsk.
I've been resetting it because I get the CEL/TractionControl/CruiseControl light combo, but I will stop immediately.
Logged again after the wastegate fix, but the spreadsheets look the same even though I clicked on A/F Correction 1/3. So that's a no go there..
I'm going to try and take it somewhere to get underneath tomorrow, but everything around here is closed for the 4 day, and Germans don't like working weekends.

thanks to both of you for the help
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Old 10-05-2012, 04:40 PM   #9
the suicidal eggroll
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2012 WRX

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Be very careful getting on the throttle after fixing the exhaust leak. If I'm right, and the exhaust leak is big enough to make the O2 read lean and throw off your closed loop corrections, as soon as the problem is fixed the car will go back to boosting like normal, so your extra tight wastegate arm is going to make you overboost.
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