Welcome to the North American Subaru Impreza Owners Club Monday March 8, 2021
Home Forums Images WikiNASIOC Products Store Modifications Upgrade Garage
NASIOC
Go Back   NASIOC > NASIOC Technical > Factory 2.5L Turbo Powertrain (EJ Series Factory 2.5L Turbo)

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 01-20-2015, 10:18 AM   #1
gsrcrxsi
Scooby Specialist
 
Member#: 236952
Join Date: Jan 2010
Chapter/Region: MAIC
Location: Baltimore
Vehicle:
2010 WRX (SSM)
Stg 2+ 310/370, 6sp R180

Default Burning up Front oxygen sensor every 6mo

Hey guys. I've been having a problem for about the last year. For some reason my car/engine/tune/something seems to be causing failures of my front O2 sensor. They seem to last about 6months before needing to be replaced again.

A little background.
2010 WRX
Stage 2"+"
-At about 103,000mi, my head gasket failed.
-During replacement, I had the motor rebuilt with forged Pistons and new bearings. (Including all necessary machine work, etc)
-Motor was put back together with a full-race header that is ceramic coated and wrapped with DEI 'titanium' heat wrap.
-The F-R manifold is a "1.5 scroll" meaning that the lower manifold is EL twin scroll and the up pipe is merged from twin to single with a stock location flange.
-The front O2 is located on the lower tube of the FR manifold, just before the up-pipe
-I also have a wideband O2 in the downpipe just after the turbine (Cobb downpipe location)

Shortly after the motor was built and re-tuned, I noticed that the car was surging at cruise. The readout from my wideband showed the AFRs fluctuating from ~12 to ~18 and would go up and down over and over when cruising at certain throttle positions/loads. I felt like I was chasing my tail looking for loose hoses and leaks, and finally narrowed it down to the front O2 causing the issue. The stock sensor had ~106,000mi on it at that point, so I said ok fine, prob needs replaced. Problem fixed, all is well.

Fast forward ~6mo to June 2014. Same issues start to pop up. Surging at cruise, fluctuating AFRs. Initially I discounted the O2 again because I had just replaced it. But I ended up replacing the sensor under warranty (the Denso sensors have a 12month warranty, FYI). I thought, maybe I just got bum sensor, it happens. Problem fixed, all is well.

Fast forward to now, 6-7mo later, and this problem has creeped up again. I've already purchased the replacement and will replace it again.

I'm using Denso 234-9035 sensors, which is the exact same sensor as OEM.

Any thoughts on what might be causing them to fail? Has anyone else had accelerated failure with the front O2 sensor on a stage 2 or more car? I do drive quite a bit so 6mo is about 15k miles for me. But still, I'd expect the sensor to last longer than that. I'm also not running any leaded fuels or oils with crazy amounts of zinc or additives that might otherwise foul the sensor. Gas primarily from Shell or Sunoco, and I've mainly been using Mobil1 0w40 oil.

I do not have an EGT gauge, but I'd expect slightly higher than normal EGTs given that the header is coated and wrapped to trap more heat in for increased efficiency. Anyone think that is the underlying cause? Or maybe the tune itself is causing higher EGTs and burning up the sensor?

Maybe even something else? I am planning to bring this up with my tuner as I'm going to have the car re-tuned anyway for other reasons. But I wanted to start a discussion on this and see if anyone else has similar experiences or thoughts.



Sent from my iPhone using NASIOC
* Registered users of the site do not see these ads.
gsrcrxsi is offline   Reply With Quote
Sponsored Links
* Registered users of the site do not see these ads.
Old 01-20-2015, 06:30 PM   #2
sebi1990
Scooby Newbie
 
Member#: 362910
Join Date: Jul 2013
Chapter/Region: MWSOC
Location: Chicago
Vehicle:
2013 Impreza WRX
White

Default

There is many causes for a o2 sensor to go bad. Is it a problem with the wiring to the O2 sensor? Or is the sensor itself malfunctioning. If you have a picture of the sensor that would help us determinate what might have caused it to fail.
sebi1990 is offline   Reply With Quote
Old 01-20-2015, 06:54 PM   #3
424wrx
Scooby Guru
 
Member#: 171948
Join Date: Feb 2008
Chapter/Region: Tri-State
Location: new york
Vehicle:
08 wrx stg3 vf52
14 legacy, 11 fozzy

Default

i had my front sensor go a while after i installed tomei el headers. they are wrapped with dei titanium.its been good since though. i used the same denso part number you did.
424wrx is offline   Reply With Quote
Old 01-20-2015, 07:35 PM   #4
gsrcrxsi
Scooby Specialist
 
Member#: 236952
Join Date: Jan 2010
Chapter/Region: MAIC
Location: Baltimore
Vehicle:
2010 WRX (SSM)
Stg 2+ 310/370, 6sp R180

Default

Quote:
Originally Posted by sebi1990 View Post
There is many causes for a o2 sensor to go bad. Is it a problem with the wiring to the O2 sensor? Or is the sensor itself malfunctioning. If you have a picture of the sensor that would help us determinate what might have caused it to fail.
It's obviously not the wiring TO the sensor plug (ie the engine harness end of the wiring) as the problem is totally alleviated by replacing the sensor.

It is definitely the sensor itself malfunctioning. i'll take a pic when i get the sensor swapped out, but it's always the same looking. nothing really noteworthy.
gsrcrxsi is offline   Reply With Quote
Old 01-20-2015, 07:41 PM   #5
gsrcrxsi
Scooby Specialist
 
Member#: 236952
Join Date: Jan 2010
Chapter/Region: MAIC
Location: Baltimore
Vehicle:
2010 WRX (SSM)
Stg 2+ 310/370, 6sp R180

Default

I actually found my old sensor (the original OEM one) this sensor had about 106,000mi on it. But failed shortly after the new motor was installed. I wouldn't put too much weight on this one.

http://i.imgur.com/NA8nzh1.jpg

The second sensor had to be sent back to Denso for warranty replacement so I don't have it.


Sent from my iPhone using NASIOC
gsrcrxsi is offline   Reply With Quote
Old 01-20-2015, 08:17 PM   #6
gsrcrxsi
Scooby Specialist
 
Member#: 236952
Join Date: Jan 2010
Chapter/Region: MAIC
Location: Baltimore
Vehicle:
2010 WRX (SSM)
Stg 2+ 310/370, 6sp R180

Default

I'd also like to add that when these sensors "fail", its not a total failure. the sensor does not trip any codes. rather it seems to start feeding erroneous AFR data back to the ECU and the ECU begins trying to compensate (incorrectly) as a result.
gsrcrxsi is offline   Reply With Quote
Old 01-20-2015, 10:19 PM   #7
CRX7
Scooby Newbie
 
Member#: 31639
Join Date: Jan 2003
Chapter/Region: RMIC
Location: Grand Junction, CO
Vehicle:
99 Impreza
White

Default

1. Do you have any exhaust leaks. Leaks before the sensor will burn them up.
2. Boost leaks? What are your AFRs?
CRX7 is offline   Reply With Quote
Old 01-20-2015, 10:36 PM   #8
gsrcrxsi
Scooby Specialist
 
Member#: 236952
Join Date: Jan 2010
Chapter/Region: MAIC
Location: Baltimore
Vehicle:
2010 WRX (SSM)
Stg 2+ 310/370, 6sp R180

Default Burning up Front oxygen sensor every 6mo

Actually. I just replaced the manifold gaskets yesterday as there has been a small leak on the passenger side header gasket for some time now.

How exactly does an upstream leak cause the sensor to burn up? I've seen plenty of people say that the leak can make the car think it's running lean, and adds fuel to compensate, and hurts MPG, but I haven't seen anything to suggest that the leak actually HURTS the sensor itself. Elaborate please.

Last edited by gsrcrxsi; 01-20-2015 at 10:56 PM.
gsrcrxsi is offline   Reply With Quote
Old 01-20-2015, 10:39 PM   #9
gsrcrxsi
Scooby Specialist
 
Member#: 236952
Join Date: Jan 2010
Chapter/Region: MAIC
Location: Baltimore
Vehicle:
2010 WRX (SSM)
Stg 2+ 310/370, 6sp R180

Default

AFRs are "normal"
14.7ish in closed loop (cruise)
11.x ish in WOT open loop
Sliding scale at part throttle open loop.


Sent from my iPhone using NASIOC
gsrcrxsi is offline   Reply With Quote
Old 01-21-2015, 12:09 AM   #10
Blackfin
Scooby Specialist
 
Member#: 361325
Join Date: Jul 2013
Chapter/Region: E. Canada
Location: Ontario
Vehicle:
2010 STi
Dark Gray Metallic

Default

Got a pic of the O2 sensor in situ (that is, as it sits on the header when mounted in the car)?

O2 sensors have some specific mounting geometry; typically, the bung should be mounted above the horizontal plane so the sensor points in a generally "down" orientation. How is it mounted on your headers?

If the sensor is facing "up" it may be susceptible to contamination and damage from condensation in the exhaust pipe settling on it when things get are warming up and cooling down.
Blackfin is offline   Reply With Quote
Old 01-21-2015, 07:33 AM   #11
gsrcrxsi
Scooby Specialist
 
Member#: 236952
Join Date: Jan 2010
Chapter/Region: MAIC
Location: Baltimore
Vehicle:
2010 WRX (SSM)
Stg 2+ 310/370, 6sp R180

Default

It is horizontal. The same orientation as stock.


Sent from my iPhone using NASIOC
gsrcrxsi is offline   Reply With Quote
Old 01-25-2015, 09:59 AM   #12
gsrcrxsi
Scooby Specialist
 
Member#: 236952
Join Date: Jan 2010
Chapter/Region: MAIC
Location: Baltimore
Vehicle:
2010 WRX (SSM)
Stg 2+ 310/370, 6sp R180

Default

Bump


Sent from my iPhone using NASIOC
gsrcrxsi is offline   Reply With Quote
Old 01-26-2015, 09:43 PM   #13
CRX7
Scooby Newbie
 
Member#: 31639
Join Date: Jan 2003
Chapter/Region: RMIC
Location: Grand Junction, CO
Vehicle:
99 Impreza
White

Default

Leak would mean less air passing, thus less oxygen, computer thinks it is running lean, adds more fuel, thus it starts to run rich. Running rich would give significant unburnt fuel which would eventually clog the sensor. This is the reasoning I've come up with and read on other sources.

In addition, any time I've had a significant leak, it has burned up my O2 sensor pretty quick. I went through 2 early on when I owned the car with some pretty significant leaks. Fixed the leaks and stopped burning O2 sensors.

If you don't have any exhaust leaks, I would look at other things which would throw off the A/F ratio. Post MAF boost leaks, or bad MAF. I've done well with just cleaning my MAF and been able to fix most of my issues by fixing intake or exhaust leaks and swapping the plugs.
CRX7 is offline   Reply With Quote
Old 01-26-2015, 10:33 PM   #14
gsrcrxsi
Scooby Specialist
 
Member#: 236952
Join Date: Jan 2010
Chapter/Region: MAIC
Location: Baltimore
Vehicle:
2010 WRX (SSM)
Stg 2+ 310/370, 6sp R180

Default

AFR readings from my wideband sensor have been normal though. maybe a tad on the lean side if anything. (in open loop)

after replacing the O2, the car seems to run richer.

kind of the opposite.
gsrcrxsi is offline   Reply With Quote
Old 01-26-2015, 10:35 PM   #15
Uncle Scotty
*** Banned ***
 
Member#: 16200
Join Date: Mar 2002
Vehicle:
OK buy Nates beans
westcoastroasting.com

Default

...it almost sounds like contaminated fuel
Uncle Scotty is offline   Reply With Quote
Old 01-26-2015, 10:39 PM   #16
gsrcrxsi
Scooby Specialist
 
Member#: 236952
Join Date: Jan 2010
Chapter/Region: MAIC
Location: Baltimore
Vehicle:
2010 WRX (SSM)
Stg 2+ 310/370, 6sp R180

Default

across 1.5 years and multiple different stations?
gsrcrxsi is offline   Reply With Quote
Old 01-27-2015, 12:08 AM   #17
Uncle Scotty
*** Banned ***
 
Member#: 16200
Join Date: Mar 2002
Vehicle:
OK buy Nates beans
westcoastroasting.com

Default

Quote:
Originally Posted by gsrcrxsi View Post
across 1.5 years and multiple different stations?

yeah...I know...but that is a weird one

maybe something you are doing that is causing this issue that you aren't thinking is causing it
Uncle Scotty is offline   Reply With Quote
Old 01-27-2015, 12:33 AM   #18
dstroy
Scooby Specialist
 
Member#: 283711
Join Date: May 2011
Chapter/Region: NESIC
Location: Newport
Vehicle:
2012 STI sedan
Black with scratches

Default

Quote:
Originally Posted by Uncle Scotty View Post
yeah...I know...but that is a weird one

maybe something you are doing that is causing this issue that you aren't thinking is causing it

Like fuel additives, or seafoaming frequently?

For sure exhaust leaks before or at the front O2 kill it quick, and new headers (ones that haven't been tanked) from the cosmoline/other gunk inside them.
dstroy is offline   Reply With Quote
Old 01-27-2015, 06:30 AM   #19
gsrcrxsi
Scooby Specialist
 
Member#: 236952
Join Date: Jan 2010
Chapter/Region: MAIC
Location: Baltimore
Vehicle:
2010 WRX (SSM)
Stg 2+ 310/370, 6sp R180

Default

I don't use additives or sea foam.

I bought the header used. No "gunk" inside it.


Sent from my iPhone using NASIOC
gsrcrxsi is offline   Reply With Quote
Old 01-27-2015, 10:01 AM   #20
Delphi
Scooby Specialist
 
Member#: 239335
Join Date: Feb 2010
Chapter/Region: W. Canada
Location: Edmonton, Alberta
Vehicle:
2011 WRX
WRB

Default

How is the grounding situation on your car? Maybe its not getting a good enough ground and is cause the sensor to die prematurely? I mean front O2 is one of the furthest runs from the ecu.
Delphi is offline   Reply With Quote
Old 01-19-2016, 11:27 AM   #21
Ashesofthewake
Scooby Newbie
 
Member#: 233900
Join Date: Dec 2009
Default

Did you ever find a solution to this issue? I am currently experiencing the same thing. 09 Wrx/tomei headers/20g swap. I am on my 3rd front 02 sensor since installing the headers. Same crazy afr swings from 10-18 when they go. Otherwise the car runs beautifully.

I am wondering if there is some weight to delphi's suggestion about the grounding. I seem to remember a grounding strap to the headers or factory heat shield? That I couldn't re-use properly when I installed the headers. It was a long time ago so my memory is a bit fuzzy.
Ashesofthewake is offline   Reply With Quote
Old 01-19-2016, 01:56 PM   #22
zore
Scooby Newbie
 
Member#: 202850
Join Date: Feb 2009
Chapter/Region: Tri-State
Location: Central New Jersey
Vehicle:
2006 WRX Limited
Silver

Default

Quote:
Originally Posted by Ashesofthewake View Post
Did you ever find a solution to this issue? I am currently experiencing the same thing. 09 Wrx/tomei headers/20g swap. I am on my 3rd front 02 sensor since installing the headers. Same crazy afr swings from 10-18 when they go. Otherwise the car runs beautifully.

I am wondering if there is some weight to delphi's suggestion about the grounding. I seem to remember a grounding strap to the headers or factory heat shield? That I couldn't re-use properly when I installed the headers. It was a long time ago so my memory is a bit fuzzy.
What kind of gaskets are you using on the header to head?
zore is offline   Reply With Quote
Old 01-19-2016, 04:31 PM   #23
Ashesofthewake
Scooby Newbie
 
Member#: 233900
Join Date: Dec 2009
Default

Quote:
Originally Posted by zore View Post
What kind of gaskets are you using on the header to head?
I have a pair of the Grimmspeed thick gaskets on there now.
Ashesofthewake is offline   Reply With Quote
Old 01-20-2016, 09:50 AM   #24
gsrcrxsi
Scooby Specialist
 
Member#: 236952
Join Date: Jan 2010
Chapter/Region: MAIC
Location: Baltimore
Vehicle:
2010 WRX (SSM)
Stg 2+ 310/370, 6sp R180

Default

Nope. Still happens. Actually need to replace it again soon
gsrcrxsi is offline   Reply With Quote
Old 04-03-2020, 01:58 PM   #25
Treslocos
Scooby Newbie
 
Member#: 502940
Join Date: Jun 2019
Default

Quote:
Originally Posted by gsrcrxsi View Post
Nope. Still happens. Actually need to replace it again soon
Hey, found the solution yet? Same exact problem as well, but while installing the new af sensor noticed a crack in the weld on my headers with carbon around it. So, I'll check there first.

Mike
Treslocos 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 02:54 AM.


Powered by vBulletin® Version 3.7.0
Copyright ©2000 - 2021, Jelsoft Enterprises Ltd.
Powered by Searchlight © 2021 Axivo Inc.
Copyright ©1999 - 2019, North American Subaru Impreza Owners Club, Inc.

As an Amazon Associate I earn from qualifying purchases.