This Normal?
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This is a discussion on This Normal? within the Tuning: Electronic Engine Management forums, part of the Tech & Modifying & General Repairs category; So i decided to check a few parameters whilst driving today, (Air Fuel learning 1, Air fuel correction) In WOT ...

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    This Normal?

    So i decided to check a few parameters whilst driving today, (Air Fuel learning 1, Air fuel correction) In WOT these values were 0.00, but whilst cruising my learning 1 was generally negative, either -3.21 or -5.61. Is this just because i'm running 93 on a 91 octane tune?

    *Kinda new to this type of thing

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    zax
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    That's fine. Your learning will only apply when you are in closed-loop. At WOT, your car is in open-loop fueling so your applied learning and correction is zero.

    In my experience, even the stock MAFv scaling is not perfect. -5.61% is a little out of what I would consider "perfect" but it's not a major concern.

    FWIW, the negative number means that your car is shortening the pulse width of the injectors to reduce the fueling output.
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    Quote Originally Posted by zax View Post
    That's fine. Your learning will only apply when you are in closed-loop. At WOT, your car is in open-loop fueling so your applied learning and correction is zero.

    In my experience, even the stock MAFv scaling is not perfect. -5.61% is a little out of what I would consider "perfect" but it's not a major concern.

    FWIW, the negative number means that your car is shortening the pulse width of the injectors to reduce the fueling output.
    I have a Cobb SF intake if that explains it, also I'm running 93 octane on a 91 map.

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    Registered User Obeisance's Avatar
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    Instead of starting a new thread, I'll try hijacking this one. My question relates to the same problem. I've read, just as Zax posted, that A/F learning of +- 5% is normal during closed loop operation. In my commute logs (https://drive.google.com/folderview?...nc&usp=sharing), I'm seeing up to 11% A/F learning on a stock (excepting uppipe) '05 wrx. I do not suspect an intake or exhaust leak since since I can build a fair amount of boost (up to what I expect is normal for a stock 2.0L) and since visual examination of the exhaust passes muster.

    My question is (having not looked at the intake tract for a plugged filter), should I suspect that my MAF needs to be cleaned? Or should I move to learning about and tuning my car?
    David - '05 WRX

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    Update: I just checked to see if the air filter was dirty (it wasn't), and I found that the connection between the filter housing (which holds the MAF) and the tube leading to the turbo was loose. This means that un-metered air could have been entering the engine. Maybe this was being corrected for with the front A/F sensor during closed loop fueling by adding fuel (fuel learning up to 11%), and been leading to my on and off P0420 (triggered by the rear O2 sensor seeing the excess fuel). Does this seem right to anyone?
    David - '05 WRX

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    Registered User Obeisance's Avatar
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    Alright, I just took a drive without hard pulls and logged. In spite of tightening the loose post-MAF intake tube, the A/F learning 1 (%) log still gave numbers above 11%. Any suggestions?
    David - '05 WRX

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    zax
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    LTFTs can be exceptionally difficult to diagnose.

    Firstly, please download this program and run it on your computer while it's connected to the Tactrix OpenPort (ignition on): RomRaider • View topic - UTILITY: Learning View (version 0.6a 03-21-09)

    At this point, I'd first suspect a vacuum leak to be the cause of your issue. Positive numbers mean the ECU is lengthening the injector pulse width to compensate for lean fueling. However, fuel pressure, sticky injectors, O2 sensor failure, and a dirty or bad MAF could easily be a primary or secondary cause.

    Before we do anything further, pull the MAF sensor and use some MAF spray or aerosol electronics cleaner to clean the MAF hotwire. There's a chance it could be this simple to resolve.
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    Registered User Obeisance's Avatar
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    Thanks for the reply, Zax. I'll run learning view later this evening and post an update. My front O2 sensor was replaced last summer (so I hope this is not the problem). We'll see. I will also turn on the CEL checker in learning view (I expect to see my usual P0420 and another code for fuel pump circuit due to me forgetting about a security fuel cutoff switch from time to time and not resetting the ecu). I'll try to get the MAF cleaned soon too.
    Last edited by Obeisance; 02-15-2014 at 06:41 PM.
    David - '05 WRX

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    I've added the learning view readout to the above link.

    Here too: https://drive.google.com/file/d/0ByG...it?usp=sharing

    Nothing too surprising here: I had seen in my logs that the IAM was pegged at 16 and the knock correction was not too severe (although I thought that what I'd seen before were just random "road noise" readings).

    I hope to try and clean the MAF tomorrow, and log again on Monday.
    David - '05 WRX

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    zax
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    Your IAM is 16, so that's good, but you have a bit of learned timing... though nothing in the load cells with which I'd be concerned.

    Clean the MAF, see if that does the trick. If not, I'd check for vac leaks.

    Are you on the stock injectors?
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    Registered User Obeisance's Avatar
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    Thanks again for your response. The injectors are stock.

    I'm not sure how to check for vacuum leaks; I expect that spraying flammable liquid (ether or some aerosol) around the intake (to see if it gets sucked in through a leak and causes the engine to rev) is a dangerous idea since the hot exhaust piping/turbo is nearby.
    David - '05 WRX

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    Quote Originally Posted by Obeisance View Post
    Thanks again for your response. The injectors are stock.

    I'm not sure how to check for vacuum leaks; I expect that spraying flammable liquid (ether or some aerosol) around the intake (to see if it gets sucked in through a leak and causes the engine to rev) is a dangerous idea since the hot exhaust piping/turbo is nearby.
    Yes. Bad idea.

    1. Compressor line
    2. Smoke
    3. Soapy water

    Pick one.
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    Registered User Obeisance's Avatar
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    Alright, I cleaned the MAF with the CRC cleaner (it didn't look dirty to begin with, but the temp sensor did so I cleaned both) and I took a 30 min drive to see if the fuel learning would greatly adjust. It didn't seem to: https://drive.google.com/folderview?...0k&usp=sharing

    I'll next try to see if I can pinpoint a vacuum leak.
    Last edited by Obeisance; 02-16-2014 at 01:34 PM.
    David - '05 WRX

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    Get a proper smoke test done with a real machine that is governed properly to not over pressurize the system.

    Sent from my SM-N900V using Tapatalk

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    zax
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    Quote Originally Posted by hybridEJ View Post
    Get a proper smoke test done with a real machine that is governed properly to not over pressurize the system.

    Sent from my SM-N900V using Tapatalk
    A regulator from a compressor should be sufficient, but I agree that a smoke test is much much simpler.

    To build on this, make sure you research how to pressurize the intake. You'll need to block off the cylinder head/PCV vents before pressurizing.
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