A/F learning 1 maxed out and P0171 CEL
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This is a discussion on A/F learning 1 maxed out and P0171 CEL within the General Maintenance, Troubleshooting & Accidents. forums, part of the Tech & Modifying & General Repairs category; -The A/F learning 1 table on the Cobb AP is maxed out at 15% while driving. Sits at 7-10% on ...

  1. #1
    Registered User wreckingball man's Avatar
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    -The A/F learning 1 table on the Cobb AP is maxed out at 15% while driving. Sits at 7-10% on idle.
    -Also a P0171 CEL will appear randomly, usually during city driving. Never appears during hwy driving. I drove about 1,000 miles hwy and the CEL never came up. I drove about 8 miles in the city on the weekend and it popped right up. I cleared the code and drove another week just hwy and the CEL never re-appeared...until I went back to city driving.

    Any ideas to get me started?
    Last edited by wreckingball man; 08-18-2013 at 11:19 AM.

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    Master Baiter EJ257's Avatar
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    How many miles on the front O2 sensor?
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    Registered User wreckingball man's Avatar
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    ^Unknown. That was one of my first thoughts, although it looks like it's new. But I guess you don't know until you change it out. Would it not also throw a "heater core low" CEL if it were bad?

    I was also thinking FPR, fuel filter, dirty injectors, MAF, or vac leak maybe.

    But all the hoses seam to be in order, except throttle body hose might have some pin-hole leaks. I cleaned the MAF and the seal is good. No pre-turbo leaks (that I can see). Ran injector cleaner.

    Cobb Stage 2 91 OTS, always using 91 octane or better. All other parameters are perfect.
    Last edited by wreckingball man; 07-25-2013 at 11:13 AM.

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    Air filter problem?
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    Registered User wreckingball man's Avatar
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    Air intake filter is new. Needed replacing anyway. Although, the CEL did go away with hwy driving after I cleaned the MAF, Injectors, and replaced air filter. But in city driving it still persists randomly.

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    zax
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    FYR, my front O2 sensor went out at approx. 105k miles. However, it was a fail/no-fail situation: when the O2 sensor failed, I had zero correction.
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    Quote Originally Posted by zax View Post
    FYR, my front O2 sensor went out at approx. 105k miles. However, it was a fail/no-fail situation: when the O2 sensor failed, I had zero correction.
    Yeah, mine died at 95k. It immediately threw a persistant CEL until I replaced it, though.

    Zach, would an exhaust leak (say at the header gaskets) possibly cause a lean detection? What if the O2 sensor was loose?
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    zax
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    Quote Originally Posted by Rambo View Post
    Zach, would an exhaust leak (say at the header gaskets) possibly cause a lean detection? What if the O2 sensor was loose?
    Yes. Absolutely. Both exhaust leaks and vac leaks will skew your fuel trims.
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    Registered User wreckingball man's Avatar
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    So it sounds that since it's not a persistent CEL, and the o2 sensor looks almost new that the more likely cause would be a vac/exhaust leak? How highly would you rank the fuel system components (FPR, filter, injectors) in the "likely culprit list?"

    Tomorrow i will go ask for a leak test on the exhaust and all the hoses. Fastech Motorsports is literally 5 miles down the road. What should I expect as far as cost (after business hours, cant call) and are these tests something i should do first?

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    Registered User wreckingball man's Avatar
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    After talking with a few different people today the P0171 is commonly an intake leak post MAF.
    Inspected the MAF ring, Air-Filter box, turbo inlet, y-pipe, and throttle body coupler. TB coupler was split and cracked. I replaced that and I will be watching the AF learning 1 table on my hiking trip tomorrow and see if this solves the problem. I drove about 5 miles today and it got up to 4.7%, so hopefully it dosn't continue to rise.

    If not, the next option will be fuel filter which is due for a change in a couple thousand miles anyway. If that dosn't work then I'm taking it to the shop for a leak test and let someone else troubleshoot this crap

  12. #11
    Registered User wreckingball man's Avatar
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    The throttle body coupler was not the source of the problem.

    I examined the front o2 sensor and it looks a little suspect. The intake manifold gasket is new (and it dosnt idle rough either) and the exhaust gaskets are all intact.

    On to the next solution, the fuel filter. It was due for a change anyway, so I picked a new one up today, installed, and reset ECU. We'll see tomorrow if this solves the problem. If not, I'll be looking towards the front o2 sensor.

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