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Old 01-20-2013, 06:16 PM   #1
veel86
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Default A/F learning and knock

If my A/F Learning varies more that 5.5% does this indicate that I have a fueling issue? I am experiencing a lot of FBKC.
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Old 01-21-2013, 09:22 AM   #2
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If my A/F Learning varies more that 5.5% does this indicate that I have a fueling issue? I am experiencing a lot of FBKC.
I would keep all your questions in your original thread so that all your info/logs are in one place. From what I recall with the logs you posted, there were not any extreme A/F Learning 1 values. Extreme would be something well outside of +/- 5%, say outside of +/- 8% or so.

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Old 01-21-2013, 09:43 AM   #3
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Okay that's my mistake thank you mine are about 6% difference.
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Old 01-21-2013, 10:37 AM   #4
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Okay that's my mistake thank you mine are about 6% difference.
Just to be clear, you are not looking at the difference between the values, you are looking at each value individually to see if it is well beyond +/- 5%.

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Old 01-21-2013, 10:58 AM   #5
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Ah... Okay my learning value C was at +6 when I looked at it yesterday
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Old 01-21-2013, 11:14 AM   #6
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Ah... Okay my learning value C was at +6 when I looked at it yesterday
That is a little borderline - I would just keep you eye on it (you can periodically check them via live data) and see if it gets worse or if another value in the other ranges starts getting extreme.

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Old 01-21-2013, 12:06 PM   #7
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Okay I will what does it mean when the values are treating then 5%?
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Old 01-22-2013, 08:53 AM   #8
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Okay I will what does it mean when the values are treating then 5%?
A/F Learning 1 is based on patterns of corrections from the front o2 sensor. If the ECU sees a pattern where it has to consistently add fuel due to a consistent lean condition (as read by front o2 sensor), then it will increase A/F Learning 1 in the current range to attempt to mitigate that problem. Same if it sees a consistently rich condition, except it will decrease A/F Learning 1 in the current range. Small corrections are normal. It is also normal to see A/F Learning 1 move around and even sometimes go from positive to negative. So, there's a general rule of thumb that anything within around +/- 5% is normal. If you are well outside that (say +/- 8% or worse), then you likely have an actual mechanical issue that is contributing to your fueling issue.

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Old 01-22-2013, 02:04 PM   #9
veel86
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Ahh okay I understand. Also this past two weeks I have gotten gas twice including today, but my gas tank will only fill up 3/4 of the way. There is some problem there I have to figure out but could whatever is causing that affect my A/F Learning values?
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Old 01-23-2013, 08:27 AM   #10
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Ahh okay I understand. Also this past two weeks I have gotten gas twice including today, but my gas tank will only fill up 3/4 of the way. There is some problem there I have to figure out but could whatever is causing that affect my A/F Learning values?
No, that shouldn't impact A/F Learning. You've seen +6% as your most extreme value? That is borderline - might mean nothing.

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Old 01-23-2013, 10:25 AM   #11
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Yes that I've seen right now A/F Learning C has been sitting at 5
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Old 01-23-2013, 10:29 AM   #12
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Yes that I've seen right now A/F Learning C has been sitting at 5
I wouldn't worry about that. Just keep an eye on all the values over a bit more time.

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Old 01-23-2013, 06:08 PM   #13
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I was +17 in bank a and +22 in b when my front o2 was dying. Now.that's extreme. Lol
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Old 01-23-2013, 07:55 PM   #14
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Damn that makes mine look fine lol. Now my A/F Learning 1 consistently moving and stays at 5.5 and my A/F Learning C is at 5.1 and I am consistently get -2 FBKC under normal driving. What mechanical problem can cause this or possibly cause this?
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Old 01-24-2013, 09:40 AM   #15
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Damn that makes mine look fine lol. Now my A/F Learning 1 consistently moving and stays at 5.5 and my A/F Learning C is at 5.1 and I am consistently get -2 FBKC under normal driving. What mechanical problem can cause this or possibly cause this?
For your car, -2 feedback knock correction is a single count - if this is occurring at low load (normal cruise-type driving) or with larger throttle changes, then it is generally just noise. We discussed in your other thread of random -6 feedback correction and the loose lower turbo heatshield - did you get that removed?

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Old 01-24-2013, 12:52 PM   #16
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Okay and yes i removed the loose turbo heat shield. While highway driving i will still get the -12 FBKC. I can't find anything rattling around or loose in the engine bay area. And because my A/F Learning 1 and C are increasing about 5.0 this indicating a fueling issue like you said before. My understanding is that the higher the value the front o2 sensor reads the more fuel is being added. I do not know my true A/F Ratio because i need to rewire the calibration wires in my innovate wide band. Do you know the possible mechanical problems that will cause these values to increase?

Thank you
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Old 01-24-2013, 07:18 PM   #17
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update:
A/F Learning C increased to 5.5 and doesn't move from there.
A/F Learning 1 stays at 5.5 under throttle.
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Old 01-24-2013, 07:28 PM   #18
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Well I looked at your other thread full of broken hoses, missing nuts/bolts, loose flashlights etc. I seriously doubt that its fueling IMHO (Anythings possible though). If someone failed to properly bolt up your downpipe as referenced in the other thread and left a flashlight under your intake they could have just as easily left a can of red bull (or the missing nuts and bolts) laying on top of your motor. If I were you I'd do a serious cleaning of the engine bay and use a mirror and your new found flashlight and crawl around looking for missing bolts, brakets, broken mounts etc., While you are at it replace all of your vacuum hoses because its sounds like you've got some dry rot going on. After that I'd make sure your knock sensor is properly torqued. Then I'd build one of these:
http://forums.nasioc.com/forums/show....php?t=2205161

and leak test it myself even though the dealership "told" you that you had no leaks.
AND THEN I'd go make some pulls. But hey thats me

Good luck
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Old 01-24-2013, 07:43 PM   #19
veel86
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I relooked over my car and the silicone couplar from the throttle body to the intercooler is torn... i haven't touched my car sense the Subaru dealership did work on it... Never going back there again. Could this be the cause for my A/F Learning to be high? My theory is that more air is being sucked through the torn couplar causeing my ecu to be adding more fuel.
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Old 01-24-2013, 09:05 PM   #20
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Yep. It can cause positive AF learning values for the reason you said (your MAF doesnt see it but your front O2 sensor does (not seeing target AFR's) thus adding fuel to correct it). Like I said before, just to make double sure of catching leaks I would build a leak tester. You only need 5 to 8 psi of pressure in the intake tract and a spray bottle with soapy water. Your car will be squeaky clean and buttoned down after you eliminate the leaks.

Last edited by nmlittlebigman; 01-24-2013 at 09:42 PM. Reason: clarify
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Old 01-24-2013, 09:11 PM   #21
veel86
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Okay good will order the part tomorrow. Thank you for your advice it is much appreciated and I will do my own leak test like you said.
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Old 01-24-2013, 09:40 PM   #22
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No problem. I had some pesky leaks that kept creeping up and I must have leak tested a dozen times over a couple months until I finally eliminated all of them. I am so retentive about leaks that I put cable ties on every connection that didn't have a hose clamp. Like you I was logging just about every other day and was working with a tuner as well.
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Old 01-24-2013, 10:45 PM   #23
veel86
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Dang I I've been doing the same thing. I have zip ties on my hoses that don't have clamps. I have a lot of zip ties haha. Those leaks are tricky.
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Old 01-25-2013, 08:31 AM   #24
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update:
A/F Learning C increased to 5.5 and doesn't move from there.
A/F Learning 1 stays at 5.5 under throttle.
Keep in mind that the +/- 5% is a general rule of thumb. Doesn't mean that a 5.1 you have a definite fueling problem. Generally, I would say that +/- 6-7% is borderline reading - keep your eye on it and see if it gets worse. +/- 8-9% - there's definitely some kind of issue. +/- 10% or worse - definitely a major problem.

-12 feedback knock correction is definitely unusual. Do you have any logs of this occurring?

Bill
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Old 01-25-2013, 12:25 PM   #25
veel86
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My A/F Learning has been getting worse over time and it had been at 6 before. I have posted logs of this occurring in my other thread.
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