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Old 05-15-2018, 01:08 AM   #626
subaru_gc8
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Member#: 29292
Join Date: Nov 2002
Chapter/Region: SCIC
Location: Orange County CA
Vehicle:
2004 WRX wagon
silver

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Quote:
Originally Posted by jawang213 View Post
having the same issue as you guys. i have an 06 wrx with a p0171 only mods i have is an AP with stage 1 91 octane tune map and a invidia down pipe heres what ive replace/checked

replaced upstream a/f sensor
replaced downstream 02 sensor
replaced leaking intake manifold gasket
swapped/cleaned MAF sensor (swapped with good reliable one)
checked fuel pressure 38-40psi 50-52psi with return line clamped
smoke tested intake system (found no additional leaks)
replaced pcv hose
cleaned throttle body
replaced air filter

noticed that this code only appears when im at idle. checked my fuel trims with obd tester and found that its sitting at max correction +25% which would indicate lean but when analyzing 02 sensor it indicates rich condition (which you can noticeably smell) looking for any ideas of anything to check or replace code came on out of nowhere no major repairs or no tune changes. please help!
Where did you buy your wide band sensor? also how do you know the MAf is good?
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Old 05-31-2018, 05:07 PM   #627
LGCjairen
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Member#: 486639
Join Date: May 2018
Chapter/Region: MAIC
Location: Pittsburgh, PA
Vehicle:
2005 wrx, 9-2x
silver :(

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to add my fix to this.
05 wrx, started throwing code and running like garbage. before i got the code i would get mild surging/hesitation at wot. after the code and running like garbage i started getting misfire codes along with the 171.
fpr/fuel pump and filter solved all of it. took that opportunity to switch the fuel filter to the engine bay like the 02-04 wrx
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Old 08-17-2018, 01:59 PM   #628
mini-minivan
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Join Date: Aug 2018
Default Damn MAF..

*REPOST FROM CEL STICKY*
Threw a CEL today, came back as PO171 said I would need a new MAF, already had injector seals replaced, but smell gas on start or on a harder pull
2008 WRX
mods:
COBB stage 1 CAI
Invidia Downpipe

note:just purchased vehicle about a week ago, am going to try cleaning out MAF but ive read that aftermarket intakes can throw a CEL for your MAF commonly. HELP
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Old 11-09-2018, 01:00 PM   #629
hamboner
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Member#: 493796
Join Date: Nov 2018
Location: Oakland, CA
Vehicle:
2004 WRX, no mods
Silver

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Not helpful to the previous poster, but mine was fixed by re-attaching the hose to the T-fitting on the BOV... I guess it popped off when I took my intercooler out. I also tightened the intercooler/turbo connection hose, which may have helped.

CEL disappeared after a hundred miles or so of mixed city/highway driving.

04 WRX, no mods
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Old 11-13-2018, 06:12 PM   #630
Gumdrop
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Member#: 430276
Join Date: Sep 2015
Chapter/Region: South East
Location: Melbourne, FL
Vehicle:
2007 Stage 2 STI
Obsidian Black Pearl

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I guess I'll add to the list to see if anyone else can help.
I am having a P0171 code on my 07 STI as well...
This code popped up after the following 3 things happened:
  1. Took car to Subaru to get fluids flushed (diff/trans/power steering/brake)
  2. Ran Wawa 93 Octane gas for the first time (I had a gift card...)
  3. Installed GD STI 08+ Steering Wheel and SWC
Relatable Mods:
  • Cobb SF Air Intake
  • Cobb Turbo-back exhaust
  • Tomei UEL Headers + Uppipe cerakote (black ceramic coated)
  • IAG Black TGV Deletes
  • Perrin silicon turbo inlet
  • Street-tuned by Mikey Botti November 2017
  • Koyo Radiator w/ Mishimoto 2 big radiator hoses
  • Crawford AOS
  • Walbro 255lph Fuel Pump
  • Grimmspeed lightweight crank pulley
Things I have tried:
  • Replaced front O2 sensor (it was replaced a few months back diagnosing a p0172-rich, but that turned out to be dirty MAF)
  • Tested MAF with someone who removed theirs (speed density), no change
  • Replaced MAF with denso, no change
  • Replaced stock fuel pump with Walbro 255
  • Replaced fuel pressure regulator
  • Replaced fuel in-tank filter
  • Replaced MAP sensor with a working one, no change
  • Replaced coolant temp sensor with a working one, no change
  • Cleaned fuel sock
  • Ran fuel system/injector cleaner in tank
  • Boost/Vac leak tested twice (once with 15psi pressurized, once with a smoke test machine) no issues
  • No noticeable exhaust leaks (had car up on lift couldn't hear or feel anything)
  • Compression/leakdown test, no issues
  • Checked ground connection on driver side of intake mani-no issue
  • Swapped injectors/coils/plugs around (since Cyl 4 was having big misfires) and misfires did not follow
Symptoms:
  • CEL P0171
  • 25% fuel corr. at idle
  • AFR up near 17/18 at idle
  • AP Boost Gauge near 10psi at idle
  • Roughness/Misfire on Cyl 4 random at idle (sometimes up to 20 counts)
  • Random small Roughness/misfire counts on other Cylinders (1-2 counts)
  • Car canít reach peak boost anymore (20psi, only getting 17psi)
  • Car runs a little richer (AFR gets closer to 14.7) at idle when AC is ON (when AC cycles it gets closer to 14.7 then drops back up to 17-18)

Last edited by Gumdrop; 11-17-2018 at 09:08 AM.
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Old 11-15-2018, 08:45 PM   #631
llDemonll
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Join Date: Apr 2012
Location: WA
Vehicle:
2006
Black

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Going through the same issue right now.

Stock 2003 WRX, 2.0T

Behavior: Car starts perfectly fine, like not even a crank of the engine before it's started; doesn't seem to have any issue idling either. Car seems to drive OK at low RPM but as soon as it gets into boost it just falls on it's face. Medium to heavy throttle will do nearly nothing and feels like the car is choking, not sure if it's a "no air" or "no fuel" choke. Light throttle (25% or less) will accelerate to highway speeds fine and drive like normal.

Haven't done a boost leak test but verified by hand that all lines are present and no obvious disconnects. Fuel filter has been replaced, shop reported that fuel pressure is 35psi and spec is 43.5 (research says this is normal, shop says it's low?)

Don't want to start spending money on parts and throwing them at the car (MAF, O2 sensor, fuel pump), but would also like to get this resolved ASAP
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Old 11-18-2018, 01:53 AM   #632
gregmyers1714
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Join Date: May 2018
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After going through the list having no sucess and completly giving up, I decided the best route would be to upgrade my way out. I went e85 so I had to replace my pump, injectors, filter, and cleaned out the hard fuel lines with an air hose, a bunch of crud came out, I'm pretty sure the clogged lines were the cause of my cel
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Old 11-19-2018, 03:17 AM   #633
aust_sti06
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Member#: 487720
Join Date: Jun 2018
Exclamation P0171 code as well as (bucking / backfire) after WOT

i know this is an old thread and im new to nasioc so i dont really know how to start my own, i just figured id ask since you all have had an idea of this problem before.

i have a 2006 subaru sti with a 20g turbo, ewg, rebuilt motor, lightweight crank pulley, lightweight flywheel, perrin turbo inlet, full invidia exhaust, grimmspeed uppipe an stock headers.TGV delete, hks bov.

When i originally rebuilt the motor over a 6 months ago i got a new denzo o2 sensor in the front and tonight i replaced my downpipe one. i also got a new 265 walbrow fuel pump when i rebuilt it. it always drove fine after i rebuilt but always almost died when coming to a stop, it didnt have any codes before an then i blew my turbo and replaced it with a 20g. every part i have installed has been tuned by my etuner. my afrs read from 17-20 afr. i have replaced intake manifold gaskets last week as well as tgv gaskets. as well as cleaned and oil my typhoon k and n intake filter. also cleaned MAF with rubbing alcohol. used a wire wheel to clean front o2 and replaced downpipe o2 today and im kind of stuck at this point, i have replaced seals to my maf and changed hose after hose just to see if it would do a difference but stil nothing. its to the point where the car is undrivable and will buck and backfire really bad after it is fully warmed up. im really confused with what is happening. my maf shouldnt be bad considering my car shuts off completely after i unplug it while idling. i was hoping someone could pleaaassee help me. i got new ngk sparkplugs when i first rebuilt it 6 months ago as well, also took coil packs to oreillys to test them an nothing really changed with the numbers on a multimeter. they all said 0. please help me
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Old 11-19-2018, 12:16 PM   #634
llDemonll
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Join Date: Apr 2012
Location: WA
Vehicle:
2006
Black

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get rid of the BOV if it's vent to atmosphere. get a recirculating DV. that will help some of the issues with stalling coming to a stop.

also, if your afr are 17-20 you're going to blow something up if you haven't already. that's super lean. WOT should be 11-12 and idle should be about 14-15

get a boost leak test done
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Old 11-20-2018, 03:05 AM   #635
aust_sti06
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So should I get a Perrin one? Also I blew my old turbo up so thatís why I got the new one lol, how do you think I can do a boost leak test? Iíve done a diy vac test but havenít found any leaks
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Old 12-03-2018, 04:45 PM   #636
Gumdrop
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Member#: 430276
Join Date: Sep 2015
Chapter/Region: South East
Location: Melbourne, FL
Vehicle:
2007 Stage 2 STI
Obsidian Black Pearl

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Quote:
Originally Posted by Gumdrop View Post
I guess I'll add to the list to see if anyone else can help.
I am having a P0171 code on my 07 STI as well...
This code popped up after the following 3 things happened:
  1. Took car to Subaru to get fluids flushed (diff/trans/power steering/brake)
  2. Ran Wawa 93 Octane gas for the first time (I had a gift card...)
  3. Installed GD STI 08+ Steering Wheel and SWC
.
.
.
just to give everyone an update.....mine was a bad driver-side (cyl 2 / 4) intake manifold/TGV gasket....idk how a smoke test and a pressurized test (to 15psi) missed it, took it to dealership and they found it by doing the 'carb cleaner' method, sprayed in the area and sure enough found the leak..

I originally started with the carb cleaner vac leak check, but didn't spray that gasket because I was afraid with injector/spark right there

All fixed and running smooth! And hey...all sensors are now replaced.....
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Old 01-08-2019, 12:53 PM   #637
ARhodes
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Join Date: Nov 2018
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Hey guys. This thread is great so thanks for starting it! I may have missed it but I didnt really see anyone with the same as me. After my car warms up from driving and I come to a stop and idle for a while the light would come on. I can clear it and it seems to drive fine. However it does seem to be idling low. It's set at 800 but idles around 700.

2005 wrx. 190k miles
Mods- perrin intake
Forge Bov
Full invidia catless dp and exhaust
Cobb stage 2
Probably more from previous owners.


Planning on getting rid of the bov to go back to a bpv but any other suggestions would be great.

Last edited by ARhodes; 01-08-2019 at 01:49 PM.
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