Welcome to the North American Subaru Impreza Owners Club Thursday August 13, 2020
Home Forums Images WikiNASIOC Products Store Modifications Upgrade Garage
NASIOC
Go Back   NASIOC > NASIOC Technical > FA Series Factory 2.0L Turbo Powertrain

Welcome to NASIOC - The world's largest online community for Subaru enthusiasts!
Welcome to the NASIOC.com Subaru forum.

You are currently viewing our forum as a guest, which gives you limited access to view most discussions and access our other features. By joining our community, free of charge, you will have access to post topics, communicate privately with other members (PM), respond to polls, upload content and access many other special features. Registration is free, fast and simple, so please join our community today!

If you have any problems with the registration process or your account login, please contact us.







* As an Amazon Associate I earn from qualifying purchases. 
* Registered users of the site do not see these ads. 
Reply
 
Thread Tools Display Modes
Old 07-22-2020, 12:52 PM   #1
dneve85
Scooby Newbie
 
Member#: 493759
Join Date: Nov 2018
Default AF Correction Spikes

So I was on an OTS tune for about a year and would notice my AF Correction 1 values jump back and forth by ~10%. This would happen while cruising with 5-10% throttle on level pavement. For example, it would drop to -10, then flash back to 0 and do so until throttle position changed or the surface of the road changed.

Fast forward to 2 weeks a go. I installed additional parts on the car and brought it into a local performance shop to do a smoke test and pressurized boost leak test. While they found a couple small leaks and fixed them, the issue is still happening. Currently I am going through an E-tune process and as most of you know, questions and then answers can take a day to hear back. So i am trying to be proactive and see if anyone here can point me to what might be going on. I did notice water in the air box about a year a go, could that have caused the MAF to have issues?


MAF and MAP sensors have been cleaned, problem still occured.

I have logs if you would like to see them.

Thanks!
* Registered users of the site do not see these ads.

Last edited by dneve85; 07-22-2020 at 01:15 PM.
dneve85 is offline   Reply With Quote
Sponsored Links
* Registered users of the site do not see these ads.
Old 07-22-2020, 01:44 PM   #2
dpetro1
Scooby Newbie
 
Member#: 487500
Join Date: Jun 2018
Location: Catonsville, MD
Vehicle:
2018 WRX

Default

I would say that +/- 10% is fairly normal especially for an OTS tune.
See where things land once the custom tune is done. While cruising +/- 5% is really spot on.
dpetro1 is offline   Reply With Quote
Old 07-22-2020, 01:56 PM   #3
dneve85
Scooby Newbie
 
Member#: 493759
Join Date: Nov 2018
Default

Disregard this reply

Last edited by dneve85; 07-22-2020 at 04:30 PM.
dneve85 is offline   Reply With Quote
Old 07-22-2020, 04:30 PM   #4
dneve85
Scooby Newbie
 
Member#: 493759
Join Date: Nov 2018
Default

Quote:
Originally Posted by dpetro1 View Post
I would say that +/- 10% is fairly normal especially for an OTS tune.
See where things land once the custom tune is done. While cruising +/- 5% is really spot on.
I don't think I was very clear. So with steady throttle, no change in load, AF correction bounces around by 10% until load changes. So going 55mph with steady throttle on a level surface, my AF Correction goes from -6 to 4 to -6 to 4 to -6 to 4, etc. or 20 to 10 to 20 to 10 etc. So while my sustained values are w/in the recommended parameters, this jumping around shouldn't be happening.
dneve85 is offline   Reply With Quote
Old 07-22-2020, 04:35 PM   #5
dpetro1
Scooby Newbie
 
Member#: 487500
Join Date: Jun 2018
Location: Catonsville, MD
Vehicle:
2018 WRX

Default

Ahh, I see
Does this just happen for a few seconds a few minutes into your trip? My car does this, tuner told me this normal behavior, some type of o2 sensor check.
If it's doing it the entire drive then there could be an issue.
Good ole anxiety port...
dpetro1 is offline   Reply With Quote
Old 07-22-2020, 04:42 PM   #6
dneve85
Scooby Newbie
 
Member#: 493759
Join Date: Nov 2018
Default

Quote:
Originally Posted by dpetro1 View Post
Ahh, I see
Does this just happen for a few seconds a few minutes into your trip? My car does this, tuner told me this normal behavior, some type of o2 sensor check.
If it's doing it the entire drive then there could be an issue.
Good ole anxiety port...
I can make it last as long as the road stays level and my foot is at the same throttle position. Doesn't seem like normal behavior to me. I can feel the fuel cutting in and out.
dneve85 is offline   Reply With Quote
Old 07-22-2020, 04:43 PM   #7
dpetro1
Scooby Newbie
 
Member#: 487500
Join Date: Jun 2018
Location: Catonsville, MD
Vehicle:
2018 WRX

Default

I would mention it to your tuner. Take a log of the problem to send as well.
dpetro1 is offline   Reply With Quote
Old 07-22-2020, 04:51 PM   #8
dneve85
Scooby Newbie
 
Member#: 493759
Join Date: Nov 2018
Default

Quote:
Originally Posted by dpetro1 View Post
I would mention it to your tuner. Take a log of the problem to send as well.
I have, and we are trying to troubleshoot it. I just wanted to reach out to the forum to see if anyone else has experienced this and if they know what it was caused by.
dneve85 is offline   Reply With Quote
Old 07-23-2020, 12:50 PM   #9
gn4rwhals
Scooby Specialist
 
Member#: 453427
Join Date: Aug 2016
Chapter/Region: MWSOC
Location: Detroit, MI
Vehicle:
2017 WRX
Crystal White Pearl

Default

If you have an aftermarket intake, check the wiring harness extension for the MAF.

These can go bad and cause erratic behavior
gn4rwhals is offline   Reply With Quote
Old 07-23-2020, 09:05 PM   #10
tegxsi
Scooby Newbie
 
Member#: 446029
Join Date: May 2016
Location: East Bay, CA
Default

AF correction1 is a short term fuel trim (STFT)... it's usually all over the place especially with sudden throttle changes. What you are seeing isn't out of the ordinary.
tegxsi is offline   Reply With Quote
Old 07-24-2020, 09:12 AM   #11
dneve85
Scooby Newbie
 
Member#: 493759
Join Date: Nov 2018
Default

Quote:
Originally Posted by tegxsi View Post
AF correction1 is a short term fuel trim (STFT)... it's usually all over the place especially with sudden throttle changes. What you are seeing isn't out of the ordinary.
I disagree with you. Can you replicate this behavior? If it's normal, why is my tuner perplexed by it and trying to troubleshoot it? It shouldn't be jumping around by exactly 10.16 every time when there is no change in the load.
dneve85 is offline   Reply With Quote
Old 07-24-2020, 09:13 AM   #12
dneve85
Scooby Newbie
 
Member#: 493759
Join Date: Nov 2018
Default

Quote:
Originally Posted by gn4rwhals View Post
If you have an aftermarket intake, check the wiring harness extension for the MAF.

These can go bad and cause erratic behavior
I am having the issue using a speed density tune too, so idk how the MAF cable would effect that.
dneve85 is offline   Reply With Quote
Old 07-24-2020, 09:43 AM   #13
Rexy18
Scooby Newbie
 
Member#: 500337
Join Date: Apr 2019
Default

Quote:
Originally Posted by dneve85 View Post
I disagree with you. Can you replicate this behavior? If it's normal, why is my tuner perplexed by it and trying to troubleshoot it? It shouldn't be jumping around by exactly 10.16 every time when there is no change in the load.
So the issue is either mechanical (car related) or tune (tuner related). You say it isnt the tune so then its your car. I would assume its the tune, and that oscillation by 10% or more happens only upon certain load/throttle request/input. Trims are adjusting because youre teetering between two cells and your tuner needs to fine tune it after he finds it.

I am tuned too and i noticed same behavior but ONLY upon very light throttle (output—so letting go of the pedal to a point the holding). It only happens sometimes when i hit the right cells and ecu adjusts accordingly. I think this happens when there is a change of load based on light throttle input, at least in my scenario. So yes, i would agree with texgsi that it is “normal “ behavior. I dont feel anything except my eyes seeing 0% then 10.17% then 0% and so on for 2-5 cycles.
Rexy18 is offline   Reply With Quote
Old 07-24-2020, 10:07 AM   #14
dneve85
Scooby Newbie
 
Member#: 493759
Join Date: Nov 2018
Default

Quote:
Originally Posted by Rexy18 View Post
So the issue is either mechanical (car related) or tune (tuner related). You say it isnt the tune so then its your car. I would assume its the tune, and that oscillation by 10% or more happens only upon certain load/throttle request/input. Trims are adjusting because youre teetering between two cells and your tuner needs to fine tune it after he finds it.

I am tuned too and i noticed same behavior but ONLY upon very light throttle (outputóso letting go of the pedal to a point the holding). It only happens sometimes when i hit the right cells and ecu adjusts accordingly. I think this happens when there is a change of load based on light throttle input, at least in my scenario. So yes, i would agree with texgsi that it is ďnormal ď behavior. I dont feel anything except my eyes seeing 0% then 10.17% then 0% and so on for 2-5 cycles.
I have seen the issue before with the MAPerformance OTS tunes. Maybe it is just something with the Subie ECU. Happy to hear someone else is experiencing this. I will pass this information on to my tuner. Thanks for the input.
dneve85 is offline   Reply With Quote
Old 07-24-2020, 11:10 AM   #15
alapilusa
Scooby Newbie
 
Member#: 424692
Join Date: Jun 2015
Location: NJ
Vehicle:
2015 WRX
WRB

Default

This has been happening to me for probably 3 years and 80,000+ miles. Usually happens within the first few minutes of my drive, but will happen rarely further into my drive. Only at very light load. I've come to ignore it over time. Has no real effect on drivability/performance, and clearly it has no issues with reliability or else I would have had serious problems by now. Its something with either the ECU specifically, or a sensor warming up/calibrating over time.
alapilusa is offline   Reply With Quote
Old 07-24-2020, 11:12 AM   #16
gn4rwhals
Scooby Specialist
 
Member#: 453427
Join Date: Aug 2016
Chapter/Region: MWSOC
Location: Detroit, MI
Vehicle:
2017 WRX
Crystal White Pearl

Default

If I understand correctly we are all seeing this:

https://datazap.me/u/gn4rwhals/weird...ata=1-2-3-7-21
gn4rwhals is offline   Reply With Quote
Old 07-24-2020, 11:44 AM   #17
alapilusa
Scooby Newbie
 
Member#: 424692
Join Date: Jun 2015
Location: NJ
Vehicle:
2015 WRX
WRB

Default

Quote:
Originally Posted by gn4rwhals View Post
If I understand correctly we are all seeing this:

https://datazap.me/u/gn4rwhals/weird...ata=1-2-3-7-21
Not exactly. There is no step up/down between changes. It just fluctuates directly between 2 values at just about 10 apart. For instance - +5, -5, +5, -5 with no values in the middle. If I remember to pay attention when I drive this weekend, i'll try to grab a log of it and post it.
alapilusa is offline   Reply With Quote
Old 07-24-2020, 02:23 PM   #18
Rexy18
Scooby Newbie
 
Member#: 500337
Join Date: Apr 2019
Default

Quote:
Originally Posted by alapilusa View Post
Not exactly. There is no step up/down between changes. It just fluctuates directly between 2 values at just about 10 apart. For instance - +5, -5, +5, -5 with no values in the middle. If I remember to pay attention when I drive this weekend, i'll try to grab a log of it and post it.
Sounds about right, about 10% swing back and forth a few times.
Rexy18 is offline   Reply With Quote
Old 07-24-2020, 02:55 PM   #19
dpetro1
Scooby Newbie
 
Member#: 487500
Join Date: Jun 2018
Location: Catonsville, MD
Vehicle:
2018 WRX

Default

Quote:
Originally Posted by alapilusa View Post
This has been happening to me for probably 3 years and 80,000+ miles. Usually happens within the first few minutes of my drive, but will happen rarely further into my drive. Only at very light load. I've come to ignore it over time. Has no real effect on drivability/performance, and clearly it has no issues with reliability or else I would have had serious problems by now. Its something with either the ECU specifically, or a sensor warming up/calibrating over time.
This is what i was mentioning in an earlier post. Tuner told me its normal so I moved on with my life.
dpetro1 is offline   Reply With Quote
Old 07-24-2020, 03:03 PM   #20
dpetro1
Scooby Newbie
 
Member#: 487500
Join Date: Jun 2018
Location: Catonsville, MD
Vehicle:
2018 WRX

Default

Wait, why do we have two threads on this now? I can't follow...
dpetro1 is offline   Reply With Quote
Old 07-26-2020, 01:17 AM   #21
keehs
Scooby Newbie
 
Member#: 517038
Join Date: Jul 2020
Default

Plus or minus 10 seems normal for an ots tbh

At least from what Iíve seen. Log it against tgv activity, does anything correlate there?
keehs is offline   Reply With Quote
Old 07-27-2020, 10:52 AM   #22
dneve85
Scooby Newbie
 
Member#: 493759
Join Date: Nov 2018
Default

Quote:
Originally Posted by gn4rwhals View Post
If I understand correctly we are all seeing this:

https://datazap.me/u/gn4rwhals/weird...ata=1-2-3-7-21
You can see what I am talking about in the beginning and end of the log. It jumps around by a variable of 10.16 with no change in acceleration or load. https://datazap.me/u/dneve85/log-159...data=1-8-11-21
dneve85 is offline   Reply With Quote
Old 07-27-2020, 12:51 PM   #23
gn4rwhals
Scooby Specialist
 
Member#: 453427
Join Date: Aug 2016
Chapter/Region: MWSOC
Location: Detroit, MI
Vehicle:
2017 WRX
Crystal White Pearl

Default

That is really odd, I see that its actually adding fuel when it doesn't need it.

Zoomed in: https://datazap.me/u/dneve85/log-159...zoom=7199-7662
gn4rwhals is offline   Reply With Quote
Old 08-01-2020, 11:20 PM   #24
emu1342
Scooby Newbie
 
Member#: 419426
Join Date: Apr 2015
Location: Florida
Vehicle:
2015 WRX
Black

Default

Thatís so bizarre. My WRX does something similar. I wonder if itís a bad O2 sensor. Weird thing is, the car runs great unless I use cruise control. Thatís when AF numbers go crazy
emu1342 is offline   Reply With Quote
Old 08-06-2020, 12:02 PM   #25
dneve85
Scooby Newbie
 
Member#: 493759
Join Date: Nov 2018
Default

That is exactly what is happening to me now. AF Learning jumps to -20 while using cruise control. No clue what the hell is going on. Hoping my tuner can work his magic.
dneve85 is offline   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump

All times are GMT -4. The time now is 07:38 PM.


Powered by vBulletin® Version 3.7.0
Copyright ©2000 - 2020, Jelsoft Enterprises Ltd.
Powered by Searchlight © 2020 Axivo Inc.
Copyright ©1999 - 2019, North American Subaru Impreza Owners Club, Inc.

As an Amazon Associate I earn from qualifying purchases.