Welcome to the North American Subaru Impreza Owners Club Sunday December 9, 2018
Home Forums WikiNASIOC Products Store Modifications Upgrade Garage
NASIOC
Go Back   NASIOC > NASIOC Technical > Engine Management & Tuning > AccessPort

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.
* Registered users of the site do not see these ads. 
Reply
 
Thread Tools Display Modes
Old 09-17-2013, 05:42 PM   #1
dawkins20
Scooby Newbie
 
Member#: 267415
Join Date: Dec 2010
Default Weird Positive A/F Learning

Hi Bill and others

I have been having strange A/F learning trims suggestive of a lean condition in cruise ranges. This is a Legacy GT 2011 Stage I Etune (etune was done due to constant mid load knock on OTS 93 map even with good gas) boost/vac leak test I did didn't find any leaks. Air Filter , intake , exhaust are all bone stock. Plugs are relatively new with less than 5k miles. No unusual oil consumption or rough idle, smoking or other strange symptoms.

A few times recently my lower load A/F learning trims have shot up into the 7s and stayed there. Most recently I have the following trims (note that the ranges are rescaled from the stock/OTS ranges) and it seems to have stabilized here, although the A range trim is pretty labile and ranges from 1-5.

A= +1.56 (0-10gm/sec)
B= +7.03 (10-50gms/sec)
C= +3.12 (50-80gm/sec)
D= +0.78 (80+gm/sec)

Of note ever since I purchased the accessport, this car has always had positive trims in all flow rates, but always staying between 2-4 and not exceeding the recommended 5%. I feel like a pre-turbo vac leak would increase the A trim the most, and since thats not the case and my leak test was negative I don't think thats the problem. Also car is hitting target boost. Car is under 40k, so failing o2 sensor or MAF seems less likely.

The only other issues I see with this car currently is a fairly consistent knock learning at 1.3-1.7 load around 3.5-4.5k rpm when ambient temps are high in 3rd gear or higher. WOT pulls are clean.

What kind of fueling or mechanical issue can i look for here?
* Registered users of the site do not see these ads.
dawkins20 is offline   Reply With Quote
Sponsored Links
* Registered users of the site do not see these ads.
Old 09-17-2013, 10:36 PM   #2
loather
Scooby Newbie
 
Member#: 367325
Join Date: Sep 2013
Chapter/Region: SCIC
Location: southern californa
Vehicle:
2008 STi Hatchback
White

Default

I'd try cleaning the MAF and HO2S. Wouldn't hurt to run a bottle of injector cleaner through the system as well. Other than that, hard to say. Might be an error in the e-tune if it's consistently overfueling.
loather is offline   Reply With Quote
Old 09-18-2013, 02:41 AM   #3
Cobb Tuning
NASIOC Vendor
 
Member#: 4803
Join Date: Mar 2001
Location: Austin, TX
Default

Hey bud! Thanks for the questions and definitely appreciate the details your provided. In general I wouldn't consider those AF Learning values to be too bad at all. The factory MAF scaling isn't always picture-perfect and things like ethanol content, air filter obstructions and MAF/O2 sensor variance/degradation will always cause small "skew" from perfect zero. That said, performing another smoke test on full the intake tract might be a good idea. If your budget allows, replacing the MAF sensor with new OEM as a sanity test is a good way to eliminate all worries.

Cheers

Lance
Cobb Tuning is offline   Reply With Quote
Old 09-18-2013, 02:37 PM   #4
dawkins20
Scooby Newbie
 
Member#: 267415
Join Date: Dec 2010
Default

Quote:
I'd try cleaning the MAF and HO2S. Wouldn't hurt to run a bottle of injector cleaner through the system as well
Already done

Quote:
The factory MAF scaling isn't always picture-perfect and things like ethanol content, air filter obstructions and MAF/O2 sensor variance/degradation will always cause small "skew" from perfect zero
Thanks for the input. I thought the COBB normal variance was considered +/-5 . I have always hovered around +2 to +5, but never had it go above this in the past. also thought it was weird that the car has never seen negative trims at all, even with all stock setup.
dawkins20 is offline   Reply With Quote
Old 09-18-2013, 04:14 PM   #5
loather
Scooby Newbie
 
Member#: 367325
Join Date: Sep 2013
Chapter/Region: SCIC
Location: southern californa
Vehicle:
2008 STi Hatchback
White

Default

positive trims could also indicate a minor vacuum leak - as Lance suggested try a smoke test on the intake and check if you see any leaks. The brake booster would be a good place to start - seems like every vehicle I've ever had a vacuum leak on the brake booster (or line thereto) was involved.
loather is offline   Reply With Quote
Old 09-18-2013, 06:08 PM   #6
nmlittlebigman
Scooby Specialist
 
Member#: 321409
Join Date: May 2012
Chapter/Region: SWIC
Location: Arrey, NM
Vehicle:
2003 Big Effing Van
7.3L powerstroke diesel

Default

Quote:
Originally Posted by dawkins20 View Post
I thought the COBB normal variance was considered +/-5 . I have always hovered around +2 to +5, but never had it go above this in the past. also thought it was weird that the car has never seen negative trims at all, even with all stock setup.
But you aren't running an OTS COBB map and your AF Learning ranges were changed, so comparing the two is not going to tell you squat.

Stock AF Learning settings typically would be: (courtesy NSFW on romraider forum)

AF Learning #1 A: 0-5 grams per second. This is idle.

AF Learning #1 B: 5-10 g/s. A little more than idle, but so low it's difficult to reach with the car in gear.[2]

AF Learning #1 C: 10-40 g/s. This covers most of your cruising.

AF Learning #1 D: 40+ g/s. This is light acceleration, or cruising uphill. There is no strict upper bound for this range, but again the switch to open loop tends to happen around 60 g/s.


Your tuner changed those settings most likely to eliminate AF fueling corrections (D range) in OL fueling. Like Lance stated above those numbers aren't too bad. I would still do another boost leak test and check the o-ring for the maf sensor just to make sure that you don't have any un-metered air coming in.
nmlittlebigman is offline   Reply With Quote
Old 09-18-2013, 07:23 PM   #7
kaczmarz
Scooby Newbie
 
Member#: 307624
Join Date: Jan 2012
Chapter/Region: MWSOC
Location: Des Plaines, IL.
Vehicle:
2008 WRX Hatch
325/347, 380XT, 8 cm2

Default

In case of my car, the "B" range gets more positive when I try to give it too much gas in higher gears (3-5) at lower RPM (below 2200). Try not to drive the car below 2200 RPM (unless on cruise control), and then check your trims and see if this works. I often get slight knock when accelerating more than just touching the gas pedal at lower RPM in higher gears. You could also check your logs for these events (slight knock when throttle position goes up at lower RPM).
kaczmarz is offline   Reply With Quote
Old 09-27-2013, 04:04 PM   #8
dawkins20
Scooby Newbie
 
Member#: 267415
Join Date: Dec 2010
Default

OK, update to this nonsense. I flashed back to the Cobb OTS 91 octane map just to have a steady reference to compare.

A/F learning ranges are Cobb map settings: A=0-10 B=10-50 C=50-80 D=80+

Drove around for a bit logging fueling parameters and noticed a few crazy things.
The B range A/F learning again worked its way up to +7 range, but the A/F correction variance is reallly all over the place. One distinct pattern that I noticed is that in cruising conditions in 3-5th gear, when the RPMs are below approx 3000 to 3200, the A/F correction is consistently pulling fuel, generally a mild amount, but occasionally having maxed out corrections to -25. This is not under boost so does not fit a boost leak profile. However, when the RPM gets over this into the mid 3000s, even under the same load, the A/F correction starts adding tons of fuel, even on top of the already lean looking A/F learning value of 7.

I tried logging this behavior a bunch on a long drive and was able to reproduce it pretty consistently, to the point where it almost looked like a bad MAF scaling, but this is with the stock intake and filter and stock injectors!!! The massive short term rich dips were more unpredictable. WOT pull still looks perfect, although it is a conservative map with 91 OTS and 93 octane gas.

Clearly I have some fueling issue, but these numbers don't fit the pattern for any specific issues I am aware of (ie, not lean under vac, rich under boost like a boost leak, not lean everywhere worse at lower flow like a post maf pre turbo leak) Any other issues this could be? I was thinking fuel pump or injectors but wouldnt that be worse under WOT when fuel demands were higher? Fuel pressure problems under low pump loads? I am at a loss. I would love some guidance from the Cobb guys or any other knowledgeable source.

Logs attached below to illustrate some of the problem areas.

Rich Dip Cruising

Rich to Lean Transition

WOT pull then rich a/f correction

(the slight timing pull in the WOT log was learned correction from before)

Last edited by dawkins20; 09-27-2013 at 04:12 PM. Reason: attach logs
dawkins20 is offline   Reply With Quote
Old 09-27-2013, 04:10 PM   #9
nmlittlebigman
Scooby Specialist
 
Member#: 321409
Join Date: May 2012
Chapter/Region: SWIC
Location: Arrey, NM
Vehicle:
2003 Big Effing Van
7.3L powerstroke diesel

Default

You didn't attach logs. Anyways if your corrections are maxing out and it is only happening in closed loop then you should suspect bad/dirty maf sensor or failing (front) o2 sensor.
nmlittlebigman is offline   Reply With Quote
Old 09-27-2013, 04:25 PM   #10
dawkins20
Scooby Newbie
 
Member#: 267415
Join Date: Dec 2010
Default

Logs attached now. Whats odd is the sensor is only maxing out extremely intermittently. It doesnt happen that often. MAF numbers look stable and dont seem to be fluctuating here, and don't bad MAFs typically underread which causes the car to go lean?
dawkins20 is offline   Reply With Quote
Old 09-27-2013, 06:55 PM   #11
nmlittlebigman
Scooby Specialist
 
Member#: 321409
Join Date: May 2012
Chapter/Region: SWIC
Location: Arrey, NM
Vehicle:
2003 Big Effing Van
7.3L powerstroke diesel

Default

Yea your maf flow looked stable. My guess is front o2 sensor getting wiggy.
nmlittlebigman is offline   Reply With Quote
Old 09-30-2013, 12:20 AM   #12
dawkins20
Scooby Newbie
 
Member#: 267415
Join Date: Dec 2010
Default

Flashed to Satge 0, stock mode, and still getting this same behavior, what could possibly cause numbers this consistently weird. Wouldnt a bad o2 sensor consistently read high or low, not swing like this from rich to lean at over 3k rpm?
dawkins20 is offline   Reply With Quote
Old 09-30-2013, 09:38 AM   #13
nmlittlebigman
Scooby Specialist
 
Member#: 321409
Join Date: May 2012
Chapter/Region: SWIC
Location: Arrey, NM
Vehicle:
2003 Big Effing Van
7.3L powerstroke diesel

Default

Could be a loose connection or frayed wire to the O2 sensor as well. A faulty or intermittent signal could cause this IMHO. Your ecu is primarily using the maf and front O2 sensor to adjust fueling in cruise (closed loop fueling (CL)). It also looks at MAP,ECT, TPS and rear 02 sensor too. However since your car is only doing this in CL it is most likely maf or front O2. Once you get into Open Loop fueling your ecu ignores the front O2 sensor.
nmlittlebigman is offline   Reply With Quote
Old 09-30-2013, 09:58 PM   #14
dawkins20
Scooby Newbie
 
Member#: 267415
Join Date: Dec 2010
Default

Swapped the MAF with a known good one from a 2011 outback, and got nearly the exact same numbers as with my MAF so that's not the problem. The only problem I have with thinking that it's the O2 sensor that's wonky is that the car has been having intermittent knock, even on the stock tune, when it is in open loop also. This problem is particularly bad at mid load mid RPM around 1.5 load and 3 to 4.5k RPM. If the O2 sensor was the issue, It shouldn't have any effect on open loop fueling.

So my thought now is an intermittent leak post MAF pre Turbo that I (and a smoke test) have been unable to find, or a fuel delivery problem, maybe pump or FPR problem. But I'm just guessing. I'm going to try a fuel pressure test tomorrow.
dawkins20 is offline   Reply With Quote
Old 10-01-2013, 09:44 PM   #15
loather
Scooby Newbie
 
Member#: 367325
Join Date: Sep 2013
Chapter/Region: SCIC
Location: southern californa
Vehicle:
2008 STi Hatchback
White

Default

i'm developing a similar condition with my car. I've smoked the intake and the trims for the C-range are around 9-14% pretty consistently. Intake tract won't hold pressure either - an attempt to pressurize it to 1.5 psi results in all the air leaking out from an unknown location.

Trims are negative until the car hits 3000 RPM when the manifold is under vacuum. Then, it must be sucking air from somewhere that isn't through the air filter as I can't find the leak. No smoke comes out anywhere I can see during the smoke test. I don't have any knock issues though.

I'm considering replacing the turbo inlet hose, as that would force me to inspect all connections and hoses to it, but seriously - $200 for a silicone hose? gtfo.

I'm going to inspect all the connections anyways and see if I can figure out where it's coming from. It doesn't seem to be post-turbo as the numbers don't line up (and I've double-checked those connections a bunch of times).

Any common problem areas I should be looking at first?
loather is offline   Reply With Quote
Old 10-01-2013, 09:52 PM   #16
nmlittlebigman
Scooby Specialist
 
Member#: 321409
Join Date: May 2012
Chapter/Region: SWIC
Location: Arrey, NM
Vehicle:
2003 Big Effing Van
7.3L powerstroke diesel

Default

Quote:
Originally Posted by loather View Post


Any common problem areas I should be looking at first?
Your on the right track. Stock turbo inlets are notorious for tearing right at the turbo. I replaced mine with a Perrin. Yes it's pricey but its a solid investment in the health of your car.
nmlittlebigman is offline   Reply With Quote
Old 10-02-2013, 09:48 PM   #17
loather
Scooby Newbie
 
Member#: 367325
Join Date: Sep 2013
Chapter/Region: SCIC
Location: southern californa
Vehicle:
2008 STi Hatchback
White

Default

Ordered that and a bunch of hose clamps - let's see if this makes a difference. Stay tuned...
loather is offline   Reply With Quote
Old 10-14-2013, 04:38 PM   #18
dawkins20
Scooby Newbie
 
Member#: 267415
Join Date: Dec 2010
Default

Quote:
Originally Posted by dawkins20 View Post
Swapped the MAF with a known good one from a 2011 outback, and got nearly the exact same numbers as with my MAF so that's not the problem. The only problem I have with thinking that it's the O2 sensor that's wonky is that the car has been having intermittent knock, even on the stock tune, when it is in open loop also. This problem is particularly bad at mid load mid RPM around 1.5 load and 3 to 4.5k RPM. If the O2 sensor was the issue, It shouldn't have any effect on open loop fueling.

So my thought now is an intermittent leak post MAF pre Turbo that I (and a smoke test) have been unable to find, or a fuel delivery problem, maybe pump or FPR problem. But I'm just guessing. I'm going to try a fuel pressure test tomorrow.
OK, repeated the smoke test and no leaks, also did the fuel pressure test and was 38psi at idle, up to 47 with FPR hose disconnected , so no problems there. Still having knock at mid load dropping DAM and having positive A/F learning across the board with -A/F correction at lower RPM swinging to + A/F Correction above 3200 RPM pretty consistently. Problems are present on both Stock and Cobb OTS maps. I am out of ideas.
dawkins20 is offline   Reply With Quote
Old 11-27-2014, 01:32 AM   #19
welaish
Scooby Newbie
 
Member#: 392151
Join Date: May 2014
Default

Use Fuel Trim to Diagnose Vacuum and Fuel Delivery Leaks. With the engine idling, look at the Short Term Fuel Trim (STFT) and Long Term Fuel Trim (LTFT) values. Normal range may be high as plus or minus 8, but closer to zero is best. If the numbers are +10 or higher for STFT and LTFT, your engine is running LEAN. Rev the engine to 1500 to 2000 RPM and hold it steady for half a minute or so. If the fuel trim numbers drops back down to a more normal reading, it confirms the engine has a vacuum leak at idle. This is because vacuum leaks have less of a leaning effect on the fuel mixture as engine speed and load increase.

If the fuel trim readings do not change much, the lean fuel condition is more likely due to a fuel delivery problem (weak fuel pump, restricted fuel filter, dirty fuel injectors or a leaky fuel pressure regulator) than a vacuum leak.

LTFT fuel trim readings that are trending high might also be the result of a slight ignition misfire that is not bad enough yet to set a misfire code but is bad enough to cause a drop in fuel economy. One or more fouled spark plugs that are misfiring occasionally, or a weak ignition coil or bad plug wire that is allowing some occasional misfires could be the cause.

You can use fuel trim readings to check the response of the oxygen sensors and engine computer to changes you make in the fuel mixture. While the engine is idling, temporarily disconnect a vacuum hose. You should see the STFT fuel trim readings jump immediately and go POSITIVE, and the LTFT should start to creep up in response to the artificial lean fuel mixture you have just created by disconnecting the vacuum hose.

To test a rich response, you can feed some propane vapor from a small propane tank into the throttle body or a vacuum hose connection on the intake manifold. This time, you should see a drop in fuel trim readings, with STFT going NEGATIVE, and LTFT creeping downward in response to the rich fuel mixture.

No change in fuel trim readings when you create an artificial lean or rich fuel mixture would tell you the engine computer is NOT operating in closes loop, or that the oxygen sensor(s) are not responding to changes in the fuel mixture.
welaish is offline   Reply With Quote
Old 01-14-2017, 01:28 PM   #20
kris142b
Scooby Newbie
 
Member#: 450777
Join Date: Jul 2016
Chapter/Region: MWSOC
Vehicle:
2002 WRX
Sedona Red Pearl

Default

Did you guys ever find out what happened
kris142b is offline   Reply With Quote
Old 12-05-2018, 11:15 PM   #21
Subaru2019wrx
Scooby Newbie
 
Member#: 494781
Join Date: Dec 2018
Default

sorry i am newb at this forum. not sure how to check for things here.

But i ask it here and see how it goes.
I thought or think i have a boost leak. i been taking dealer and they just check oil and the clamps are on tight. and just shoooo me away.
Finally i told them i would pay for a AFR test.

First off they only did idle AFR which does nothing for me for checking for leak. which i will go tomorrow and have them do.

But my numbers right now for idle are
STFT is. -.08
LTFT is. -7
mass air flow is 2.8
with the formula for calculating AFR it about 15.1

Even just looking at the LTFT that is really low for idle. That almost confirms that i have a boost leak i feel like. but they said anything under 10 is OK. well mines is like 3 away from that. And that "10" percent i feel like is average after idle.

My question is just looking at the numbers is -7 for idle too low. Which make my car run lean.

reason i thought i had boost leak is it feels like it dosent pull like it use to. It back fires at high rpm. and some time take little more gas when clutching in first gear.

if anyone can help me on this. thanks

2019 wrx stock
Subaru2019wrx is online now   Reply With Quote
Old 12-06-2018, 12:08 AM   #22
GlarryHoodDIT
Scooby Specialist
 
Member#: 460907
Join Date: Jan 2017
Chapter/Region: RMIC
Location: Colorado
Vehicle:
2016 WRX

Default

What is an AFR test?

What are you using to diagnose fuel trims? Long term trims of 7% are normal on the DITs even stock, at least in terms of AF Learning 1. When your car is idling it's using closed loop fueling and relying on your O2 sensor for input, it's working to get back to lambda, so unless your O2 sensor is failing you're not running lean. That's why your car is correcting, to stop you from running lean or rich.

Accessport?
GlarryHoodDIT is online now   Reply With Quote
Old 12-06-2018, 02:30 AM   #23
Subaru2019wrx
Scooby Newbie
 
Member#: 494781
Join Date: Dec 2018
Default

Quote:
Originally Posted by GlarryHoodDIT View Post
What is an AFR test?

What are you using to diagnose fuel trims? Long term trims of 7% are normal on the DITs even stock, at least in terms of AF Learning 1. When your car is idling it's using closed loop fueling and relying on your O2 sensor for input, it's working to get back to lambda, so unless your O2 sensor is failing you're not running lean. That's why your car is correcting, to stop you from running lean or rich.

Accessport?
Well it the formula
mass air X (stft x ltft) devide by 14.65 = the difference of 14.65. AFR

So my AFR is about 15.1

also it is -7 I should see some positive numbers with turbo should i not. Also when it neg it is rich not lean.
Postive means lean and not rich.

I am going tomorrow to have them check at 2500 rpm so if the LTFT goes more neg then i for sure have a leak.
But i was wondering -7 is just 3 away from not being ok at all. If it was -10 then i would have got ratio of 16.3 afr which is way to rich.
But isent 15.1 at idle too rich for a stock wrx bone stock. the ECU and everything.
Subaru2019wrx is online now   Reply With Quote
Old 12-06-2018, 03:09 AM   #24
GlarryHoodDIT
Scooby Specialist
 
Member#: 460907
Join Date: Jan 2017
Chapter/Region: RMIC
Location: Colorado
Vehicle:
2016 WRX

Default

What formula are you referring to? You're posting in the Accessport section, are you getting your values from an Accessport? What Short term fuel trims and Long term fuel trims are you referring to? AF Learning 1 and AF Correction 1?
GlarryHoodDIT is online now   Reply With Quote
Old 12-06-2018, 11:34 AM   #25
Subaru2019wrx
Scooby Newbie
 
Member#: 494781
Join Date: Dec 2018
Default

Quote:
Originally Posted by GlarryHoodDIT View Post
What formula are you referring to? You're posting in the Accessport section, are you getting your values from an Accessport? What Short term fuel trims and Long term fuel trims are you referring to? AF Learning 1 and AF Correction 1?
this if off not access port. this is from the dealer ship. I dont have a cobb accessport. i am full bone stock. If i had accessport i would have to remap the car regardless. even if it a OEM flash. i would void my warrenty. So the way i found out was through dealer ship when i pay 159 dollars for a AFR test.

The formula is the one i posted up my last post. it to get the AFR difference.

This is fromLTFT B1 and STFT B1

they gave me the LTFT B1 STFT B1 and also the mass air flow and the oil temp and coolent temp. but that not what i care about. just the three values to get the difference from 14.6

Last edited by Subaru2019wrx; 12-06-2018 at 03:53 PM. Reason: not b2 but b1
Subaru2019wrx is online now   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 03:23 PM.


Powered by vBulletin® Version 3.7.0
Copyright ©2000 - 2018, Jelsoft Enterprises Ltd.
Powered by Searchlight © 2018 Axivo Inc.
Copyright ©1999 - 2017, North American Subaru Impreza Owners Club, Inc.