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Old 11-07-2012, 02:30 PM   #1
afohlin
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WRB

Default 02 WRX P0171 Problem

I have unfortunately have the dreaded P0171 in my 02 WRX. I've been doing a lot of reading on the issue and there are such a wide array of problems I'm not sure of what to do next. Only mods I have are Perrin crank pully, K&N short ram intake and Invidia turbo-back exhaust.

. My car just just under 150k miles and was running awful, pulsing when I would get on the throttle, and wasn't idling the best. I cleaned the IACV out and put in a new gasket (even though the old one was fine), changed spark plugs since I'm pretty sure they were the originals, and also changed the fuel filter. I have a K&N short ram that has been on the car for at least 6 years and I re-oiled the filter about a month ago. The MAF was really dirty so I clean it with MAF cleaner. When I was changing the spark plugs I noticed two hoses were disconnected either side of the car, so I reconnected and hose clamped them on so they wouldn't come out. I looked into it and they were just the breathers that connect to each other and run through the line in front of the intercooler so that shouldn't have been the source of the problem either. After about 100 miles the CEL came back on and was P0171 still. After all those changes the car was running the best it has in a long time and was driving like there were no issues anymore.

I was wondering what my next course of action should be. I checked to make sure no lines were blatantly unhooked but didn't see any except for the breather hoses. Is there a diagram or even a checklist of all vacuum lines to check? Would it be a good idea to pull the intercooler and check all of the lines for leaks? I don't know anyone who could swap MAF's for a day but should i just buy a new one and if the code doesn't go away return it? Another idea I had to was put the stock air box setup back in, even though the car has been running great for years with the K&N setup. Also, to check the front O2 sensor could I do the CEL fix and put a resistor where the plug is and see if it goes away? Any and all help is appreciated, thanks!
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Old 11-07-2012, 03:09 PM   #2
AkSooby
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WRB

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I think that with those mods you should have some kind of Engine Management ..I just installed a short ram intake on my 02 wagon and after driving for 20 min i got the p0171 ..I guess my car didnt like it..
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Old 11-07-2012, 03:53 PM   #3
super_usdm
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1993 Legacy SS

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Smoke test to check for more vaccum leaks. Those unhooked breathers were not so good. That's a post maf vaccum leak meaning you were pulling unmetered air into the turbo while those lines were open.
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Old 11-07-2012, 11:45 PM   #4
filmsquad
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U check ur gaskets on the turbo back exhaust u might need to get thicker gaskets from grimmspeed. Ur maf did u clean the smaller diodes this is something i did not see the only diode i saw was the big one until i saw the two smaller ones which needed much cleaning and that solved my issue after replacing ,cleaning evrything related to the p0171 code
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Old 11-09-2012, 08:51 PM   #5
afohlin
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Thanks. Ill check the exhaust for leaks and put new gaskets in. My buddy has a vacuum tester I will try also
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Old 11-09-2012, 09:41 PM   #6
Jackie leggs
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If you do go the route of replacing the MAF, don't skimp out and get one at a parts store. get an OEM. I got one from NAPA and it would max out in the cold air and throw the CEL daily till i swapped back to one from Subaru.
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Old 11-15-2012, 03:36 PM   #7
afohlin
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I didn't take the exhaust off but i checked everything out and it doesn't look like there is an exhaust leak. The car also doesn't act like their is one. I checked the vacuum hoses again and the passenger side valve cover breather hose came off again. I sent to Subaru and got a new hose but I can't get the old one out. It snakes through a bunch of stuff. Does anyone know what I have to take off to get that hose out and get a new one in? Thanks

Also I feel like the car is running the best run in a long time. Really getting on my nerves that it still is throwing the code.
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Old 11-15-2012, 04:57 PM   #8
rdowner22
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I'm sure it's probably that your MAF sensor is bad... Do you have any local tuning shops? Being a friendly shop would help, but see if they can throw one on their and then see how she's running.
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Old 11-15-2012, 05:41 PM   #9
WRX2EVOX
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Intake manifold/tgv gaskets are also a cause. Look for oil residue on the top of the heads
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Old 11-15-2012, 05:53 PM   #10
BugeyedBandit
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^ If you have oil on top of the heads directly underneath the intake manifold, is that a sure sign of bad IM or TGV gaskets? I have 2 small pools of oil there and get the P0171 code once in a while. I haven't gotten it lately though
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Old 11-15-2012, 06:24 PM   #11
Uncle Scotty
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no wonder so many of these cars get blowed sky high....
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Old 11-15-2012, 06:34 PM   #12
HinshawWRX
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