2.5T exhaust sensor diagnosis

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2.5T exhaust sensor diagnosis

Postby bigBADbenny » Fri Dec 04, 2015 10:13 am

My Lib is at 230klm, its probably due for new front and rear exhaust sensors.
No cels, just old age, my LV's are not exactly what I'd call stable...
Occasional FLKC and > -5% AF1 corrections...

BtSsm_LV_20151203_2323.png
BtSsm_LV_20151203_2323.png (50 KiB) Viewed 2461 times


Staying on top of the relaibility equation, I recently replaced the inlet pipe, TB hose and cyl3 coilpack, leaving new stock plugs and checking exhaust sensors on the to-do soon list.


These are available as genuine items from the dealer for megabucks, from Partsouq for somewhat less, or very affordably via Amazon using the generic Denso part #...
The latter being somewhat of an unkown quantity as regards compatibilty with the postFL EJ255...
This is what I found on Amazon: front a/f 234-9120 rear o2: 234-4732

Its all good swapping parts but I want to be sure of the whats and why's so I asked for some advice on LGT.
I was advised to log the following parameters:

AFR
A/F Learn #1 Fuel Learn LTFT
A/F Correct #1 Fuel Correct STFT
A/F Learn #3
A/F Correct #3
Rear O2 voltage
Rear O2 heater voltage
Rear O2 heater current
CL Fueling Target

All good and I even added these to my btssm using ecu specific custom fields.
However the resulting data is still fairly obscure to me, even after lots of googling.

So instead I used my Tactrix to log a similar spec car with almost similar mods and more importantly the same similar tune, a Throttlehappy 3 boost level SI drive controlled drivability/reliability tune... Dom's 100klm MY08 tbSTi wag.

I'm in the process of dissecting the logs we made, but heres a composite of both cars doing 100kph on the freeway, Doms is iirc on the left, mine on the right.
I'll post links to the full image and logs, and dissect some areas for greater clarity, eg warmup, hitting boost and freeway.

Here's my log, warmup, suburban, freeway:
https://www.dropbox.com/s/bwtlr8ygpsx6w ... 5.csv?dl=0

And Dom's with a similar drive cycle:
https://www.dropbox.com/s/8q2690i97b9l7 ... 7.csv?dl=0

So far I think my sensors may be ok, any advice is most welcome.
In the meantime I'll continue looking for boost/vac leaks and get the new plugs in, before seeking a retune.

Heres a side by side screenshot on the freeway, we're both at 100kph.
https://www.dropbox.com/s/2qqelu9oiz3lf ... y.jpg?dl=0
I forgot to log closed loop fuelling target, so I may reboot the process with that parameter...

Also MegaLogViewer has automatic graph rescaling so a far more accurate view will be gained from editing the logs, which is the next step.
For example I need to remove warmup from Doms log to get like for like scaling of eg AF1 resistance.

dom>ben freeway.jpg
dom>ben freeway.jpg (206.52 KiB) Viewed 2457 times
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bigBADbenny
 
Posts: 10420
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Location: Collingwood, Melbourne
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Real name: Ben Richards
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Re: 2.5T exhaust sensor diagnosis

Postby alexeiwoody » Sat Dec 05, 2015 9:10 am

I have a brand new OEM genuine Subaru/Denso front O2 sensor, just landed from Japan. I bought a spare - yours for $250

My last one died after 14 months (poor fuel economy, fuel trims out etc, then finally CEL)

I'm overseas at the moment, so I haven't put it up for sale officially yet. Let me know if you want it :)

Rear sensor doesn't do anything according to anyone in the know, so I wouldn't worry about it?
Running no. of weeks without breaking something in the lib: 0
No. of things still to fix in in the lib: 97
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alexeiwoody
 
Posts: 1900
Joined: Thu Jul 12, 2012 11:47 pm
Location: Melbourne
Car: MY07 LibGT 5EAT
Real name: Alexei

Re: 2.5T exhaust sensor diagnosis

Postby bigBADbenny » Sat Dec 05, 2015 10:53 am

Defo eoi that thanks :)

It will be interesting to compare the before and after logs, thus the purpose of this thread...
User avatar
bigBADbenny
 
Posts: 10420
Joined: Tue Oct 04, 2011 6:36 pm
Location: Collingwood, Melbourne
Car: MY07 GT-B 6MT OBP Wagon
Real name: Ben Richards
Profile URL: http://tinyurl.com/agvbzop


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