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Mehpic
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8,162 Posts
Discussion Starter · #1 ·
got a check engine light. had the code read. P0171. did some reserch on teh interwabs and found out it's a generic code for a cyllander running lean.

steps taken so far:
put stock exhaust back on (more for sanity's sake- magnaflow cat back + 50 mile daily commute = no bueno)
cleaned MAF sensor (way dirty)

next steps:
new O2 filter
new fuel filter.
i.e. cheap fixes to start- i think both of these will set me back $30.

anything else i should try?

oh, it's a 03 WRX with 112k miles on it running full synthetic oil changed every 4k miles.
 

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Mehpic
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8,162 Posts
Discussion Starter · #4 ·
mymilkexpired said:
could possibly be related to your plugs.. bit of a stretch though.

Talk to the folks over here: http://forums.nasioc.com/forums/

well, they probably do need to be changed. apparently it's a royal PITA to change plugs on my car.
 

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Was the code read with a generic type code scanner? Sometimes there are code in the system that a generic won't read that may be more specific.

Plugs are unlikely contributors to a lean condition (rich yes,lean notsomuch).
O2 sensor supplies the reading of fuel mix so that has potential.
MAF was a good idea as an inaccurate reading @intake could trigger a lean fuel mix.
Do the fuel filter for good measure.
you may also try some fuel sytem typre cleaner which will help in the event of injector pluggage.
 

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Mehpic
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Discussion Starter · #8 ·
HIMEHEEM said:
Was the code read with a generic type code scanner? Sometimes there are code in the system that a generic won't read that may be more specific.

Plugs are unlikely contributors to a lean condition (rich yes,lean notsomuch).
O2 sensor supplies the reading of fuel mix so that has potential.
MAF was a good idea as an inaccurate reading @intake could trigger a lean fuel mix.
Do the fuel filter for good measure.
you may also try some fuel sytem typre cleaner which will help in the event of injector pluggage.

cool! thanks! glad i'm on the correct track
 

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Eddy 53:11
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3,158 Posts
Try Amsoil injector cleaner. It can't hurt.
 

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HIMEHEEM said:
you may also try some fuel sytem type cleaner which will help in the event of injector pluggage.
I'm agreeing with this ^ one. Especially if you've never changed your plugs! (Over-oiling the K&N may also be a contributor).

FYI: changing plugs is not so bad. My Subie has similar mileage to yours. I've changed the plugs myself every interval. Make sure to use the proper plugs. I.e. not necessarily those recommended by Autozone/NAPA/Advance.

Get rid of the K&N. Buy a normal (cheap) air filter. Replace with every oil change. I can't tell from your post - when you say K&N, is that the whole intake, or just the K&N filter element with the standard air-box?

Not related, but very important in WRXs, esp 02 & 03: when did you last change your gearbox oil?
 

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Mehpic
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Discussion Starter · #14 ·
dave2pvd said:
I'm agreeing with this ^ one. Especially if you've never changed your plugs! (Over-oiling the K&N may also be a contributor).

FYI: changing plugs is not so bad. My Subie has similar mileage to yours. I've changed the plugs myself every interval. Make sure to use the proper plugs. I.e. not necessarily those recommended by Autozone/NAPA/Advance.

Get rid of the K&N. Buy a normal (cheap) air filter. Replace with every oil change. I can't tell from your post - when you say K&N, is that the whole intake, or just the K&N filter element with the standard air-box?

Not related, but very important in WRXs, esp 02 & 03: when did you last change your gearbox oil?
yes, the whole K&N intake. i think there's antoher co that makes a better cone style filter that'll work with it.

gearbox, as in transmission? at about 75k i think.
 

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Eddy 53:11
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I can't see how?? Never heard that though.
 

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Eddy 53:11
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The turbo primarily cares about oil and exhaust gas. I ran Amsoil on my
twin turbo with no issues.
 

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Eddy 53:11
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Have you ever changed the original plugs? I do mine about every 30-40k
but, I'm a little anal. The plug change is not as bad as you think. I have
an 04' I've done plugs in and most of the time is spent removing/getting to
the plugs themselves. If you do the plugs, get NGK's. I think mine were
Champion = sucks.
 

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Mehpic
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8,162 Posts
Discussion Starter · #19 ·
JetSpeed said:
Have you ever changed the original plugs? I do mine about every 30-40k
but, I'm a little anal. The plug change is not as bad as you think. I have
an 04' I've done plugs in and most of the time is spent removing/getting to
the plugs themselves. If you do the plugs, get NGK's. I think mine were
Champion = sucks.
stock NGKs? what about some of the fancier bosch plugs?

plugs were changed at about 50k if i remember correctly.
 

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2cflyr said:
stock NGKs? what about some of the fancier bosch plugs?

plugs were changed at about 50k if i remember correctly.
Avoid fancy!

Go on Nasioc and see what the consensus is. Your Subie is very plug-fussy.
 
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