Welcome to the North American Subaru Impreza Owners Club Sunday July 13, 2014
Home Forums WikiNASIOC Products Store Modifications Upgrade Garage
NASIOC
Here you can view your subscribed threads, work with private messages and edit your profile and preferences Home Registration is free! Visit the NASIOC Store NASIOC Rules Search Find other members Frequently Asked Questions Calendar Archive NASIOC Upgrade Garage Logout
Go Back   NASIOC > NASIOC Technical > Factory 2.5L 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.
* Registered users of the site do not see these ads.
Reply
 
Thread Tools Display Modes
Old 01-21-2013, 06:12 AM   #1
Ilovecugars
Scooby Newbie
 
Member#: 299442
Join Date: Oct 2011
Location: Southern Ontario Canada
Vehicle:
2005 Forester XT

Default Idel afr unsteady

Hi guys.
I have a 05 Fxt with a stage 3 setup and a pro tune through AP. The car have been like this for a while and has worked well. However lately it has had rough idel and has been a tough one for me to figure out.
At idel is the only time it does this, the rpm are steady within about 50rpm either way. But monitoring the afr I see it is jumping around a fair bit. It will fluctuate from 14 to around 15.5 and anywhere in between and when it jumps around it is causing a roughness felt through out the car. Once the car is rolling it has no issues and works great and even seems to improve a bit when the AC is on and has no idel issue when it is cold warning up on high idel.
I was having some surging issues at part throttle so I replaced my front o2 which did solve that issues but did not fix the idel. At least I can narrow it down to know that sensor is not at fault.
If any one has any suggestions of where to look for causes to this problem it would be a great help. The only ideas I have at the moment are perhaps a leaking bpv as it is stock or maybe a bad maf sensor. Both of which I can switch from my wifes car to rule those out.
One again any one with experience with this some help would be awesome.
Thanks
* Registered users of the site do not see these ads.
Ilovecugars is offline   Reply With Quote
Old 01-21-2013, 06:14 AM   #2
Ilovecugars
Scooby Newbie
 
Member#: 299442
Join Date: Oct 2011
Location: Southern Ontario Canada
Vehicle:
2005 Forester XT

Default

I posted this in the tuning section in the AP category as well but I don't think there is a lot of traffic there so I thought it might be best to try and ask this here.
Ilovecugars is offline   Reply With Quote
Old 01-21-2013, 07:41 AM   #3
tuzzio
Scooby Specialist
 
Member#: 292532
Join Date: Aug 2011
Chapter/Region: NESIC
Location: Southwick, Ma
Vehicle:
05 STI
PSM

Default

I'd assume that you have a vacuum leak. You should be around 14.5 at IDLE. Is your BPV/BOV leaking under vacuum?
tuzzio is offline   Reply With Quote
Old 01-21-2013, 08:51 AM   #4
Leafy
Scooby Specialist
 
Member#: 330625
Join Date: Aug 2012
Chapter/Region: NESIC
Location: MA
Vehicle:
2006 WRX
WRB

Default

Oscillating idle afr is normal. It'll also do it in cruise. This is how closed loop systems work. But it shouldnt mess up your idle. I would just check for vac leaks and post maf leaks before going back and making your tuner fix it.
Leafy is offline   Reply With Quote
Old 01-21-2013, 11:24 AM   #5
Ilovecugars
Scooby Newbie
 
Member#: 299442
Join Date: Oct 2011
Location: Southern Ontario Canada
Vehicle:
2005 Forester XT

Default

I don't really think the tune is to blame as it has worked well for awhile on this tune. I know what you mean about the afr changing slightly at idel but it seems to be having lean spikes and that is when it is felt thought out the car.
I have checked for vac leaks already but I could have missed it, if there was a vac leak tho would I not see a high number in the a,b,c,d fuel learning tables?

I'm waiting on a new bpv ago I will be able to rule that out in a few days.
Ilovecugars is offline   Reply With Quote
Old 01-21-2013, 11:31 AM   #6
tuzzio
Scooby Specialist
 
Member#: 292532
Join Date: Aug 2011
Chapter/Region: NESIC
Location: Southwick, Ma
Vehicle:
05 STI
PSM

Default

Unplug your MAF sensor and see if problem occurs. If it doesn't occur, it's a vacuum leak.

Also, it's IDLE*
tuzzio is offline   Reply With Quote
Old 01-21-2013, 11:47 AM   #7
Ilovecugars
Scooby Newbie
 
Member#: 299442
Join Date: Oct 2011
Location: Southern Ontario Canada
Vehicle:
2005 Forester XT

Default

Okay thanks I'll try that.

Hmm its seems even tho I'm on a smart phone it doesn't help my bad spelling.
Ilovecugars is offline   Reply With Quote
Old 01-21-2013, 03:39 PM   #8
Ilovecugars
Scooby Newbie
 
Member#: 299442
Join Date: Oct 2011
Location: Southern Ontario Canada
Vehicle:
2005 Forester XT

Default

Okay, I tried the test of unplugging the maf and running the car and this is what I have found.

When I unplugged the mad and start the car which was already warmed up the afr were locked at 14.7 andthe car ran smooth as can be. However after about 45 seconds then the car comes out of what I assume to be a sort of warm up closed loop and the afr starts to change up and down then the car started to run rough again.

Then I shut the car off plugged the maf back in and started the car again. Again the afr is locked at 14.7 and runs smooth as can be until it comes out of that warm up cycle and the afr start to fluctuate and then its almost instant it starts to run rough. So maf plugged in or unplugged there is no difference.

However I feel like I am getting closer to the problem with the roughness starting as soon as the afr's can fluctuate. But at this point I'm not really sure where to look next.
Ilovecugars is offline   Reply With Quote
Old 01-21-2013, 03:43 PM   #9
Leafy
Scooby Specialist
 
Member#: 330625
Join Date: Aug 2012
Chapter/Region: NESIC
Location: MA
Vehicle:
2006 WRX
WRB

Default

Can you log open loop/closed loop state? Or not even log it, just read it? I bet its coming out of its start up open loop, and when it enters closed loop it has the problem. That would point to an issue with a sensor that is in use while the car is in closed loop but not open loop, IE the O2 sensor.
Leafy is offline   Reply With Quote
Old 01-21-2013, 04:01 PM   #10
Ilovecugars
Scooby Newbie
 
Member#: 299442
Join Date: Oct 2011
Location: Southern Ontario Canada
Vehicle:
2005 Forester XT

Default

Yes I can do that, is the open loop on off category on the ap the same open loop we are taking about? So you are saying that when its first started its in an open loop at that set 14.7afr and then when it goes into closed loop is when the afr can fluctuate, that makes sense then.

I just replaced the front o2 less than 1000km ago and the car had the issue then and there was no improvement. Is there any other sensors I should check that could be at fault?
Ilovecugars is offline   Reply With Quote
Old 01-21-2013, 04:02 PM   #11
Leafy
Scooby Specialist
 
Member#: 330625
Join Date: Aug 2012
Chapter/Region: NESIC
Location: MA
Vehicle:
2006 WRX
WRB

Default

If it start to fluctuate in closed loop and doesnt do it in open loop it can only be the o2 sensor. The sensor could be fine though, it could be a wiring issue.
Leafy is offline   Reply With Quote
Old 01-21-2013, 04:18 PM   #12
Ilovecugars
Scooby Newbie
 
Member#: 299442
Join Date: Oct 2011
Location: Southern Ontario Canada
Vehicle:
2005 Forester XT

Default

Okay I'll have to start checking out the wiring and see what I can find.
This may be a dumb question but I might clear somethings up for me, if the car is in closed loop at idle and runs rough is the a reason why just cruising down the road in closed loop the afr are steady and everything is nice and smooth. The idle also improves when the AC is on, why does a bad working sensor seem to improve when there is load on the car? That is the only thing I can't get my head around.

Btw thank you for the help trouble shooting, things like this is not my strong point.
Ilovecugars is offline   Reply With Quote
Old 01-21-2013, 04:28 PM   #13
Leafy
Scooby Specialist
 
Member#: 330625
Join Date: Aug 2012
Chapter/Region: NESIC
Location: MA
Vehicle:
2006 WRX
WRB

Default

That brings up a good point about cruise, I dont know. And the AC part I've seen it before and cant explain why it happens. The afr varying from 14 to 15.5 is not that bad a little bit wide than you normally see with properly functioning closed loop. The hunting idle is the weird one. I wonder, when its hunting idle is the spark advance changing or the throttle plate position changing.
Leafy is offline   Reply With Quote
Old 01-21-2013, 04:45 PM   #14
Ilovecugars
Scooby Newbie
 
Member#: 299442
Join Date: Oct 2011
Location: Southern Ontario Canada
Vehicle:
2005 Forester XT

Default

That is what I found rather odd, from everything I've read its fairly acceptable to have your idle afr fluctuate up to one whole point and the rpm is very steady that had never been an issue. I have found if I up the rpm at idle it does improve but still not as smooth as it should be. I do see the ignition timing fluctuate a few degrees at idle, but I don't believe that will change the afr. I could be wrong tho.
Ilovecugars 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 02:20 PM.


Powered by vBulletin® Version 3.7.0
Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.
Powered by Searchlight © 2014 Axivo Inc.
Copyright ©1999 - 2014, North American Subaru Impreza Owners Club, Inc.