UGH P0171
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This is a discussion on UGH P0171 within the General Maintenance, Troubleshooting & Accidents. forums, part of the Tech & Modifying & General Repairs category; Well i have the infamous P0171 CEL. Rough idle, crappy power, the usual. Checked every line i can think of, ...

  1. #1
    Registered User GarrettKoonsman's Avatar
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    UGH P0171

    Well i have the infamous P0171 CEL. Rough idle, crappy power, the usual. Checked every line i can think of, no leaks in sight. Cleaned my MAF, tried clearing the code and trying again. The plugs are only 10k old, same with fuel filter, brand new fuel pump. Only recent change was putting a 90 amp alternator on. So i guess im either missing something or its an injector or O2 sensor or....i have no idea.

    Taking it to the shop tomorow to have it looked at. Just thought i would share the end of my day with all my Subaru friends that know these problems better than anyone
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    Registered User teflon_jones's Avatar
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    Well sorry to hear it. You checked the right places so far. Could there be a small leak you didn't notice maybe on the underside of a hose?

    The MAF may just be faulty too so cleaning it won't help. Your oiled intake may have done it over time.
    Scott
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    Registered User GarrettKoonsman's Avatar
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    Its definitely possible i missed a leak, tough to tell in my dark garage when its cold out. And my though is the MAF is bad, i just have a feeling that is it. Hopefully its not an injector but i guess whatever it is it needs fixed so who knows. On another note.. is it possible that the new alternator could affect it, possibly sending too much power to a sensor?? Also, should a new alternator be loud? This one seems to be very loud, not really whining as much as a humming noise.
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    Registered User teflon_jones's Avatar
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    Why did you put in that alternator instead of a stock one? As soon as you start messing with things like that, you can cause problems...

    I still have the stock alternator from my STi if you're interested.
    Scott
    Past Subies - '11 STI Limited stage 1+ and '04 STi stage 2+
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  6. #5
    UnBanned Sinister's Avatar
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    did you clean the MAF or the IAT bulb? very common to clean the IAT bulb and not the actual MAF wires
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  7. #6
    Registered User GarrettKoonsman's Avatar
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    Stock alternator from Subaru is 300+ stock STI is 500+, replacement WRX from Oreilleys is 220+, replacement STI from Oreilleys is $120. Honestly, I cant afford the extra couple hundred dollars on a simple fix. I now may be regretting that but i'll let you know if i need the alternator. Kevin, i did make sure to clean the actual MAF, though i had to do a double take to remind myself of the difference as i didnt the first go round.

    Well as crappy as it is i am taking my car into a shop right now. I really dont have the time this week to diagnose it myself. My days consist of 8am at the latest to 8pm at the earliest. Guess we will find out soon enough
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    Registered User GarrettKoonsman's Avatar
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    So a mixture of a few loose/cracked vacuum lines and a valve that i cannot remember the name of (IACV sounds right but they said it could have gotten crushed when changing the alternator??) were supposedly the culprit. Part has to come in tomorow so it will be in the shop over night and fixed by tomorrow afternoon as long as nothing else is wrong. So far the damage is $250.
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    Supporting Member yamaha_rider619's Avatar
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    Not too bad, hopefully that is the problem.
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  10. #9
    Moderator Donkey's Avatar
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    The IAC valve is on top of the throttlebody. I'm thinking you broke the EVAP soleniod,which is right behind the alternator.
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  11. #10
    Registered User GarrettKoonsman's Avatar
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    Quote Originally Posted by Donkey View Post
    The IAC valve is on top of the throttlebody. I'm thinking you broke the EVAP soleniod,which is right behind the alternator.
    That sounds right....I have had so much crap going on that i cant keep my facts straight. So EVAP soleniod was broken, couple loose vac hoses, one cracked hose, and hopefully thats it. They are fixing it tomorow and smoking it all again to check for additional leaks then i should be able to pick it up. Overall im pretty happy as a bad O2 sensor or MAF would have added to the cost dramatically.

    Now to just figure out how to get 2 cars home with just me.....hmmmm. All i know is even driving a supercharged V8 trailblazer does nothing to ease the despair (sp?) of not having my Subaru

    /most depressed post i have ever had
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