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Old 03-10-2008, 05:23 PM   #101
CirrusWRX
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Missed some of the responses in this thread- sorry for the late replies, fell off my radar screen. These are just random WILD guesses to take em for what they're worth (as in, nothing.)

wrxrex - were you ever able to figure your issue out? I would've gone with another fuel filter in the event the one you installed might've been bad and possibly blocking fuel resulting in a lean condition? Any chance you plumbed it backwards and reversed the In/Out?


Rodwrx23 - Yours sounds like you tried a bunch of things, but maybe I'm missing it, it sounds like you didn't check out your FRONT o2 sensor which is what PAWRX's problem was.


justinh595 - The only thing that would seem to make sense in the trans area would be a fuel line - have you ever noticed any fuel puddles or smells or leaks around that area? (I'm talking UNDER the car). Can't think of any reason the trans would affect anything P0171 related, but obviously, lots of stuff to knock loose when fiddling to get all the ancilliaries out of the way for the swap. Wouldn't be anything stupid like you forgot to plug it in or a stripped wire or something?


maengelito - The problem with an airbox that isn't completely sealed is that the air potentially getting into the engine that isn't being filtered resulting in dirt/debris finding it's way into the combustion chamber. If you're saying it seems pretty tight, there is probably a small chance, but still not a great idea. Plus your MAF isn't getting clean air so there is the potential for damage.

That said, my brother on his 1997 outback has been running without 1 clip (broke off) for about 5 years, so take it for what it's worth. Theoretically the car should idle fine so long as there isn't a major crack or gap in the aribox. But your best long-term bet would be to either find and replace the clip (order it online maybe?) or go to a junkyard and grab one, or if it's the plastic part that broke, get a whole replacement airbox from a junkyard or somebody switching to a cold air intake.

People with the P0171 problem frequently idled fine, but that didn't mean all was well in their case.



Hope some of what I read helped! Good luck!
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Old 03-19-2008, 05:11 PM   #102
Rodwrx23
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Thanks for the feedback man. I really appreciate it. I too forgot about this thread seeing as how I got rid of my P0171 just after that last post I made. The last thing I did was add a grounding kit and fixed the ground from the tranny to firewall and swapped plugs too. Still no P0171. I can't thank you enough for this thread man and helping me get rid of it.

Now, to make you laugh.

I cleaned my engine yesterday and after some cruising to the bank for work I got P0134 and P0030. I just had to laugh because I didn't swap the darn front 02 sensor out and got rid of the P0171 and now this. I'm sure the engine cleaning has nothing to do with it but I'm thinking the plug might have gotten wet or something. We'll see.
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Old 03-23-2008, 11:37 AM   #103
neuhate9999
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just some more info. i had a txs bov that i found was letting unmetered air into my intake at idle causeing me to throw the p0171 code. i put my stock air by-pass valve back on and the code went away.. took me about a month to find it...
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Old 03-23-2008, 09:08 PM   #104
aboothman
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Probably been listed on here already, but I had two issues that caused this CEL.

One was the turbo to inlet connection, which is a no brainer. The other was a crosspipe gasket.

After some careful thought (regarding the obvious), any leak before the front O2 sensor could cause this CEL. One way to narrow down the location is to log AFR and boost, while watching for knock of course. If the car hits full boost at the normal RPM, then it is a pre-compressor (vacuum) leak. If the car is late getting to boost, then it is a pre-turbo exhaust leak.

This is not the best way, and it can be risky if you have a really bad leak, but I did not have any issues. My AVC-R was adjusting the wastegate duty cycle constantly to account for boost spikes. The factory BCS, or a GM 3-port, will also maintain the factory overboost protection. I would not recommend this using an MBC, but if you do then turn down the boost well below your target boost when logging. You will still be able to determine if boost onset is taking longer than it should.

Anyway, my boost was not consistent, which was another symptom. Now that the issue is fixed boost onset is quicker, and it holds where it should with no spiking.
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Old 03-30-2008, 04:45 PM   #105
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I want to share my experience with this CEL. A few weeks ago I dropped an 18G, Deatschwerks 750s, Perrin EBCS, and an STi TMIC in my 05 WRX. I popped this code after about 120 miles of driving, while idling at a red light. Started doing some research and found this thread. The car was driving fine, and beside the CEL the only noticeable problem was a rough idle. I ran through this checklist and ruled out these problems with no luck:

1. Cold air intakes. (dont have one)
2. Stock airbox not sealed. (pulled the box, checked, resealed)
3. Hose leaks, generic air leaks. (checked & reclamped TMIC hoses, turbo inlet, intake)
4. Fuel pressure regulator. (connected, hose looks fine)
7. MAF sensor gone bad/dirty. (pulled & cleaned)

Because of the idle problem, my next guesses were the IACV or a problem with the DW 750s. The injectors were sitting for about 3 months before I installed them and the plastic bags they came in had a bit of a yellow film on them. I figured maybe DW didnt clean them thoroughly enough and something had gunked them up. I picked up some fuel system cleaner and was waiting to run my tank almost empty to put it in (per the directions on the bottle). Yesterday I turned the car on to run to the store, and no CEL. Hmmmm....The idle still seemed a little rough, but the car was cold. When I got to the store I let the car sit and the idle was better. I couldnt feel the vibration through my seat and the shifter like before. It seems like my problem is gone. The only thing I can think of is that the injectors were the culprit. Whatever was blocking them up must've broken down and been passed out. Im still going to run the fuel system cleaner through the car to be sure, but I cant think of any other cause that would eventually go away.
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Old 03-30-2008, 06:39 PM   #106
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I got this code on my ap, came on nasioc to find out what it was. then when i checked under my hood the actual filter on my spt intake had came off.
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Old 04-05-2008, 08:43 PM   #107
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I'm a subaru tech and ive also seen very small cracks in stock flexpipe that you dont even think are there. The heat shield kinda sound deadins the noise so look for black soot in the heat sheild at the seams that built up over time. moisture will kinda make it run out the bottom. Sometiems these ecu's can be fussy over the smallest glitch most people just clear it till it comes back which could be awhile. smoke testing the exhaust can be a fast problem solver. Aftermarket uppipes will throw po171 also if the car isnt tuned especially on wrx's not so much on the sti cause of the not catted uppipe. You should tune your car as you put on bolt ons. I tell most people who shouldnt own sti's but do buy an accessport lol .

Last edited by Putty; 04-05-2008 at 08:59 PM.
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Old 04-11-2008, 08:20 AM   #108
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I just wanted to say thanks to Cirrus for a great, informative thread. I've had P0171 for a while, and finally got tired of it. After seeing this thread, and at the advice of some friends on another forum, I started cheap and cleaned the MAF, ran some Seafoam through on my last fillup, and reset the ECU again.

So far, so good! Previously when I've reset the ECU, the CEL would usually come back within 50-75mi, with the most I've gotten being 150mi. Right now I'm at 350mi with no negative signs at all.

My mileage has also increase by about 3mpg so far, and seems to be getting better still. I had noticed it dropping before I even developed the CEL, but just wrote it off as the car getting old (145K). Didn't even put the 2 issues together until this thread.

Oh, and in case anyone is interested, my only mods are an STi TBE, K&N air filter, and GP Moto silencer delete pipe.

Thanks again for the great thread! I hope mine is taken care of for good, and everyone else in this thread has as good a luck as me!
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Old 04-11-2008, 11:07 AM   #109
ogboot
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i have come to terms with my p0171, but there may be a light at the end of the tunnel. If i reset my ecu it will only come back on when i hit the highway after ~10-12 miles. Driving around town for days won't make it come back. Well, i replaced the crappy BOV that was on the car when i bought it with a stock BPV and after I drove it to the store the CEL went away!!! But then it came back. So i'm thinking it has something to do either with the return hose to the intake from the BPV or the intercooler hoses. Hopefully sunday i can do some digging and find it
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Old 04-11-2008, 03:45 PM   #110
aboothman
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Well, that makes sense. If you are allowing air in after the MAF sensor, it will cause you to run lean. Hell, even if you have air coming in after the heads but before the AFR sensor, it will LOOK like you are running lean, and you may run rich as the ECU adds fuel to try and correct what it sees as an issue.
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Old 04-25-2008, 11:40 AM   #111
CyborgX_CZ
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Nice I see this thread going on for few years; well here is another “lucky” owner of P0171 CEL. My car was protuned with 20g, PE850cc bigger TMIC , walbro 255, anyway before I went protune I was on romraider map, my car was ridiculously rich , average gas mileage was 230 per tank after tune I’m getting around 300 per tank. Everything was fine for 3 weeks until now. First cell I got Monday on HWY cruise control set on 70mph. It just came on. Since then I am getting same code aprox. Every 100 miles. Right now I logging my car with EvoScan since this is only program which allows me to log my LM1 wideband with my stock O2. After reading this thread I will check everything it was said above but I think my problem will be related to stock O2. I will keep you posted and for anybody interested here is my today log which I stopped right after I got another CEL.

PS: Some of those values are in metric (temperature is in Cesium, speed is in KM/h and stock O2 is LAMBDA)

EvoScanDataLog_2008.04.25_08.13.54.csv

Currently troubleshooting with my tuner...
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Old 04-28-2008, 11:36 AM   #112
CyborgX_CZ
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Ok, no CEL today but it was also little bit colder today and also no CEL during this weekend and I was abusing my car little bit. Only what I done I clean my MAF sensor. I will keep you posted.
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Old 04-28-2008, 11:44 AM   #113
CyborgX_CZ
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So I just receive a call from my tuner and he told me my O2 sensor going bad. I send him bunch of logs I done past weekend and since I have also wideband he was able to compare stock O2 and my LM1 and that’s what seems to be a problem. So I will try replacing that one and we see.
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Old 05-28-2008, 12:55 PM   #114
b4rstiwsnc
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I had this code pop up numerous times lately, mostly at idle (could it be due to a CEL spacer on the dp which moves the o2 sensor up around 1 inch from the dp? or the CAI?) however, under wot the wastegate sounds like it is shut, boost rises to target boost 1.2-1.3 but the car does not pull like stg2, but rather stock or a bit slower than stock. It feels like the car is pulling timing under WOT. help please

mods: catless dp, injen cai, cobb ap stg2 OTS
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Old 05-28-2008, 03:46 PM   #115
CyborgX_CZ
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What tune you have?
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Old 05-28-2008, 03:48 PM   #116
CyborgX_CZ
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I will be replacing my o2 sensor this Saturday and then I see if that was really my problem or not. I hope it was cuz I just look everywhere and I can find anything suspicious
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Old 05-28-2008, 04:06 PM   #117
b4rstiwsnc
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off the shelf map
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Old 06-04-2008, 11:07 AM   #118
CyborgX_CZ
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Fourth day with out of cell but I did few things so now I will never figure out what was the problem. Changes I done:

- New O2 sensor
- Fixed small exhaust leak on down pipe when it connect to up-pipe
- New tune by Tim Bailey
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Old 06-04-2008, 01:38 PM   #119
ogboot
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Just an update to post 109. I assumed that the CEL that came back was my p0171 again, but it was actually for EGT sensor malfunction when i got the code read. Did the EGT resistor fix and all is good, that was over a month ago. So, removing the BOV and replacing it with a stock BPV alleviated my p0171.
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Old 06-15-2008, 12:39 PM   #120
MConte05
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I am fairly certian my p0171 woes are coming from a leaking exhaust before the o2 sensors. As I have a low idle and sometimes has stalled out, runs perfectly fine everywhere else.

Any suggestions on how to identify where the leak is?
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Old 06-16-2008, 12:57 AM   #121
arch4life
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so, a p0171 issue for you guys. help me out please!

i had the code about 3 months ago. if i cleared it it would come back fairly quickly, within 50-90 miles.

i replaced the front o2 sensor, oem part, 170bux.


that was march. this is june.

The p0171 code is back.

doing some datalogging, my wideband (innovate lc-1) is reading 10-11:1 afr's when cruising, while the stock o2 sensor is reading 14.7:1 or 14.8:1. the front o2 sensor seems "locked" in its output for extended periods of time on my logger, sometimes its cycling through different readings, then it goes 14.8 or 14.7 for like 10-20 lines, solid.


the front o2 sensor is dead again? i'm planning on measuring the voltage to the heater circuit to see if its overvolting the o2 sensor and eventually burning it out after 3 months. any other ideas? why would it fail 5k miles later? this is depressing!.

what else can cause the o2 sensor to fail? im debating getting an EGT gauge but i believe extreme temps would be required to burn out a sensor like that, i doubt my egt's are that high.

could things like oil on the metal casing of the sensor and the wires mess with the signal at all and cause this problem? its all sheathed, so i was assuming probably not.

the o2 sensor first gave out while i was driving, and when it gave out my afr's on my wideband fell to 10-11:1. a hour or so later, the o2 sensor woke back up or somthing because my afr's went back to 14.7:1 when cruising. then a hundred miles later, bam, its back, 11:1 afr's.

this would explain the bad gas mileage people were experiencing with this code

but anyway, any ideas? its awfully weird. i cant see how the sensor would fail like that again.
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Old 06-16-2008, 01:12 AM   #122
kirkeemonster
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Wow... mine came on for the first time ever... I had my timing belt+tensioners replaced about 500 miles ago, no problems there... so after the track (dragging) car still running fine, go home, park it, hour later start it, drive on the freeway for an hour, and BING, pops on... Im shaking my head like "...what the ****....what could it be?" After 2 days of not driving the car and finally running the code, it's the p0171.. I have an egt gauge and it reads fine, BUT, the temp on my gauge cluster is a bit lower than half way (where it usually is) sooo... what's the problem?

I do know I need to replace my fuel filter, think this is the problem?

I cleaned my maf, checked all hoses, and checked for any wierd noises.. nothing too out of the ordinary... also, im tuned (reflashed) and have a short ram on... but never had this happen before, thing from the timing belt stuff that im no longer tuned and perhaps the tuner disabled the CEL/ made me run better but with the new maintanace my cars' like "...." ?? Help!! I could disable the CEL via obd scanner but if it's something serious, im afraid.

mods:
sti up pipe
titek dp
espelir cb
FULL catless
gp moto sri
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Old 06-17-2008, 09:49 AM   #123
CyborgX_CZ
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I learn, only if I give my car enough time to check everything, analyze and compare then I get my P0171 so if I was driving inside of city (constantly changing speed and RPM) nothing happened but soon as I got on HWY after 30 minutes constant cruise speed I got that CEL. But like I said, since I change my O2 + fix little leak on down pipe and retune my car, CEL is gone. Since I did three things I can say what was my problem but my first choice will be that leak and then O2 sensor and last my tune.
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Old 06-17-2008, 08:52 PM   #124
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same. ^^^ the driving around then cel thing.
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Old 07-14-2008, 02:12 PM   #125
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I have a general question about this code- which I am battling also- why would a leak before the MAF (Airbox not sealed for example) trigger this code??? I would think the MAF reads all air coming in, and its temperature, regardless of where it is coming in from...

Thanks-
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