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Old 07-11-2012, 06:24 PM   #1
DerekDaniel
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Default A/F learning #1 consistently declining

Hello Nasioc ppl,

Quick question every time I data log my car the A/F learning 1 values is consistently declining. It started at 0 then -1.2, then -2.5 and so forth now it is down to -6.25. What could cause this and should I be concerned?
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Old 07-11-2012, 06:29 PM   #2
itsover9000
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I'm kind of new to this but i believe if the numbers are negative its adjusting by removing fuel. If its positive numbers its increasing fuel. I would say its decreasing fuel because you might have a intake air leak somewhere in your system.
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Old 07-11-2012, 07:32 PM   #3
DerekDaniel
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Yeah Thats what I thought so I just ordered a cobb post maf hose. I am hoping my MAF sensor isnt jacked up. I cleaned it the other day safely though just spraying some MAF cleaner on it.
AT what number negative value in the A/F learning does it become an issue with the car?
Also, could this cause the car to stall eventually if it is continues to reduce fuel?
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Old 07-12-2012, 09:23 AM   #4
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Quote:
Originally Posted by DerekDaniel View Post
Yeah Thats what I thought so I just ordered a cobb post maf hose. I am hoping my MAF sensor isnt jacked up. I cleaned it the other day safely though just spraying some MAF cleaner on it.
AT what number negative value in the A/F learning does it become an issue with the car?
Also, could this cause the car to stall eventually if it is continues to reduce fuel?
A/F Learning 1 will vary when driving. There are actually 4 different values that make up A/F Learning 1. When you log that parameter, you are seeing the current one being applied. You can view all 4 individually by looking at the A, B, C, D versions of the parameter. Generally, you should be within +/- 5% for each range, with outside of +/- 8% being a possible problem. You are on the borderline there, but you really want to get a good amount of driving in there since you last reflashed a map, reset the ECU, or disconnected the car's battery (all of which cleared the learned parameters of the ECU).

Positive values mean that the ECU is added fuel due to a perceived lean condition (negative means the ECU is removing fuel due to a perceived rich condition). When MAF sensor go bad, you tend to end up with large positive corrections as you airflow is underreported and you go lean. Intake tract leaks of various sorts can go either direction (generally the same with front o2 issues).

Extreme corrections aren't generally going to cause issues as long as it isn't a bad front o2 sensor. Those corrections are actually most likely helping a car than hurting it because they are getting it closer to where it needs to be fueling-wise (hopefully partially overcoming the effect of the mechanical issue). When they are extreme, though, you really want to get it fixed ASAP. In your case, you -6.25% is borderline. I would continue to watch them and see what happens over time.

Bill
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Old 07-13-2012, 03:26 PM   #5
DerekDaniel
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Default Pulls with A/F learning ABCD

Car 08 Legacy GT auto
Hello I took two data logs with learning 1 and ABCD to see if I have any issues due to the consistently declining A/F learning i was receiving. I tightened some hose clamps, and had a catback exhaust put on. It seems as if the A/F went down on the first pull but the second pull it went back up to -6 range. Bill can ya tell if anything is out of whack and be of concern? Thank you

1st pull https://docs.google.com/spreadsheet/...HZsSEd3NmtQRkE

2nd pull https://docs.google.com/spreadsheet/...2ZWanFlRWVWZXc

Also I took some regular logs and noticed that my fine knock learning has increased to -4.2 now in the 6k rpm range. It never really got in that high rpm range, before I had the catback put on.

These are also my first logs with the catback on. Notice the fine knock learning at the 6 k rpm range was lower on the first pull -1.05 but the second pull was way worse -4.2?? IS THIS BAD? Should I reset my ECU? any advice is greatly appreciated

1st pull https://docs.google.com/spreadsheet/...HNNUVBFb25XZ1E

2nd pull https://docs.google.com/spreadsheet/...XIySi1ZeW1iSnc

Why would my fine knock learning start getting worse? should I reset the ECU and see if it was possibly false knock learned? I just added a magnflow custom catback could that be causing it due to louder noise?

Last edited by DerekDaniel; 07-13-2012 at 04:19 PM. Reason: added info
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Old 07-14-2012, 08:54 AM   #6
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Hi - I responded in your other thread.

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Old 09-16-2012, 01:51 PM   #7
uk2006wrx
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Quote:
Originally Posted by DerekDaniel View Post
Hello Nasioc ppl,

Quick question every time I data log my car the A/F learning 1 values is consistently declining. It started at 0 then -1.2, then -2.5 and so forth now it is down to -6.25. What could cause this and should I be concerned?
Did you resolve your negative a/f learning 1 values? What was causing them?
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Old 09-17-2012, 01:58 AM   #8
morgue
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I having the same issue... built leak tester, fixed the few I had, reset ECU and still huge corrections in he A/F learning table.

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Old 09-17-2012, 09:43 AM   #9
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Originally Posted by morgue View Post
I having the same issue... built leak tester, fixed the few I had, reset ECU and still huge corrections in he A/F learning table.

Those are not huge corrections. If you are within about +/-5%, you are fine. Just because they are all trending negative, does not mean there is a specific issue. I would just keep an eye on them over time.

Bill
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Old 09-17-2012, 01:43 PM   #10
uk2006wrx
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How about these then from my stock 2006 wrx!!!

Quote:
A/F Learning #1:

0 - <5.60 5.60 - <10.00 10.00 - <40.00 40.00+
-14 -13.1 -6.2 -4.7
Can't find cause, any DIY checks?

I have learning view/romraider. I have pulled PCV hoses/oil filler and this swings the trims the other way running lean at idle, so I think the O2 is working ok. I think if I can solve this at idle the other ranges will resolve themselves. New air filter, and cleaned maf wire correctly.

Last edited by uk2006wrx; 09-17-2012 at 01:51 PM.
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Old 09-18-2012, 09:11 AM   #11
Cobb Tuning
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Quote:
Originally Posted by uk2006wrx View Post
How about these then from my stock 2006 wrx!!!



Can't find cause, any DIY checks?

I have learning view/romraider. I have pulled PCV hoses/oil filler and this swings the trims the other way running lean at idle, so I think the O2 is working ok. I think if I can solve this at idle the other ranges will resolve themselves. New air filter, and cleaned maf wire correctly.
A pressure or smoke test of the intake tract would be your first step here to check to see if you have any post-MAF leaks.

Bill
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Old 09-19-2012, 12:23 PM   #12
uk2006wrx
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I've checked all clamps/hoses, and even switched turbo->intercooler hose, admittedly I have nt done a boost leak test as I need to get a compressor and make a kit.

would n't a post maf leak under vacuum, cause positive fuel trims, as the ecu would need to add fuel due to the extra unmetered air?
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Old 09-19-2012, 01:10 PM   #13
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I'm curently investigating the o2 sensors as I'm wondering if they are incorrectly reporting rich to ecu.

Should the rear o2 on a 2006 wrx oscilate rich/lean continuously on idle?

Mine seems to stick 0.8V or 0.05v, unless it is reved where it will rise or fall and return.

I've NOT got a CEL or any fault codes. I'm using romraider logger graph to monitor.
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Old 09-20-2012, 09:25 AM   #14
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Quote:
Originally Posted by uk2006wrx View Post
I've checked all clamps/hoses, and even switched turbo->intercooler hose, admittedly I have nt done a boost leak test as I need to get a compressor and make a kit.

would n't a post maf leak under vacuum, cause positive fuel trims, as the ecu would need to add fuel due to the extra unmetered air?
Yes, but you can also lose metered air due to a boost leak, which would cause you to run rich and see negative fuel trims. A pressure/smoke test should always be your first test when you start seeing extreme fuel trims as post-MAF leaks are very common problems and they are the easiest (and typically cheapest) to fix compared to other possible problems like a bad MAF or front o2 or other mechanical fueling related issues.

The rear o2 only generally has limited authority over fueling and will only impact the closed loop fueling target. It has nothing to do with your long-term fuel trims related to A/F Learning 1, which is entirely due to feedback from front o2.

Bill
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