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  • Runs PREMIUM gas only (91/93octane) and has NOT had O2 sensor issue

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  • Runs PREMIUM gas only (91/93octane) and HAS had O2 sensor issue

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  • Runs any other gas and has NOT had O2 sensor issue

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Just following a hunch, so humor me :

9K views 11 replies 6 participants last post by  MTBFisch 
#1 ·
After being told that my cats are essentially doing their job and heating up to optimal temps to burn off exhaust correctly, and that my O2 sensors are effectively working and measuring what they are supposed to be measuring, I can't help but feel like the missing link is that the results O2 sensors are sending are not meeting standards of the parameters in ECU. I was told about an ECU flash, but nobody knows anything about it...I can't help but wonder if a different fuel burn might be enough to get back inside those parameters.
I'm doing fuel treatment, solely based on the mileage and service maintenance that it's ready for anyway, but at the same time, I'm running 93 through it for a bit to see if
(1) the issue will correct itself on its own or
(2) I can clear the code and it not resurface

In the mean time, I wanted to gauge whether or not there's a consistency of the issue showing up between those who only use premium vs those that don't.
 
#2 ·
How about humoring us and telling us what code(s) you're car is setting, what year/model your car is, and whether or not you even own one that's discussed on this forum (put it in your profile's signature so we don't have to ask, again). :facepalm:
 
#5 ·
Oopos...sorry, folks. Didn't realize how little info I added :

  • Owned 2009 Acadia SLT AWD for 4 yrs, taking it from around 40k to 111k. O2 codes have been in the picture for at least the last year to year and a half.
  • Original O2 sensors.
  • The codes are below and I'll preface by saying I haven't read them myself for a while, so I am not completely sure that ALL of them were there back then, but as of this morning, these are showing :
CURRENT FAULTS -
P0087 - Fuel Rail/System Pressure - Too Low
P0141 - O2 Sensor Heater Circuit (Bank 1 Sensor 2)
P0420 - Catalyst System Efficiency Below Threshold (Bank 1)
PENDING FAULT -
P2097 - Post Catalyst Fuel Trim System Too Rich (Bank 1)

This is the first time I remember seeing the P0087 or the P2097, and I'm pretty sure this is the first time I've seen a "Pending fault".

I'll also add that, right at a week ago, I had some routine service maintenance performed (flushed coolant, transmission, diffs/transaxle, PS and spark plugs all changed out), and I also started my side of this experiment by running the last 2 (previous and current) tanks with 93 octane AND Lucas Fuel System and Injector cleaner/lubricant in each tank.
I had planned on getting through at least 3 tanks before clearing faults, if they were still there, but since I was connected to the reader, I went ahead and cleared them, so we'll see what happens in the next couple days, as far as which, if any, come back.

As stated elsewhere, the dealer recommended changing O2 sensors about a year or so ago, but also stated that it wasn't an immediate threat. When I reopened the can of worms again a couple weeks ago, I went to an exhaust shop I'd used in the past, thinking it'd be easier to just replace O2 sensors AND cats (couldn't hurt), but their diagnostic was the one that found cats were heating up to optimum temps and seemingly getting the job done, and that the O2 sensors were at least running current through them. Tech said he started researching, based on that, and found something about the ECU reflash. But that got me theorizing that I might be able to just get parameters of the burnoff back into specs if running cleaner.
 
#7 ·
rbarrios said:
youre saying that youve had a CEL light on and off- for 1 to 2.5 yrs--- and you didnt change out the O2 sensors?
Correctamundo, although more like 1-1.5.
Once determined that the codes were all based on O2 sensor issue...it is not uncommon for a vehicle to be run on O2 sensor faults for quite some time without any issues aside from possibly minimal efficiency losses.
And, at the time, the $1-2k (dependent on removing the sensors without damaging the threads in cat, per the dealer), was not an option.
 
#8 ·
In my mind- you want to fix Oxygen sensor codes asap-- as to avoid damaging the cats $$$. (and pass emissions tests if in such an area.)



At 100,000--- I removed my Oxygen sensors (all 4) and replaced them.
I was not getting CEL codes or anything.
But to avoid lazy sensors and damage to the expensive cats-- I just replaced them (along with plugs, struts, front brake pads, etc.)

Cost was $180 for all 4.
Car running great--- I want to keep it that way


old and new sensors







 
#9 ·
rbarrios said:
In my mind- you want to fix Oxygen sensor codes asap-- as to avoid damaging the cats $$$. (and pass emissions tests if in such an area.)
And it's likely I could just replace the O2 sensors still at this point, what with the exhaust tech saying cats were operating properly...I guess I might just see if the O2 codes pop back on and move from there.
For what it's worth, since you pointed it out, I'm in Arkansas, where there is ZERO emissions testing...probably the main reason for no motivation to move forward with repairs.
 
#10 ·
MTBFisch said:
And it's likely I could just replace the O2 sensors still at this point, what with the exhaust tech saying cats were operating properly...I guess I might just see if the O2 codes pop back on and move from there.
For what it's worth, since you pointed it out, I'm in Arkansas, where there is ZERO emissions testing...probably the main reason for no motivation to move forward with repairs.
The motivation is that ignoring check engine codes for a year and half usually leads to more expensive repairs down the road.
 
#11 ·
divotdug said:
The motivation is that ignoring check engine codes for a year and half usually leads to more expensive repairs down the road.
I have trouble ignoring them for a day. I've had work done while I'm away on vacation due to fear of engine damage making the drive home. We had a brand new subaru that went into limp mode, turned out to be gas with very high ethanol content, subaru dealership in South Carolina took all the fuel out of the tank and put a little fresh fuel in. After a short while driving with good fuel, and a few clean engine starts, the CEL went out and limp mode deactivated.
 
#12 ·
Nvr2loud said:
I have trouble ignoring them for a day. I've had work done while I'm away on vacation due to fear of engine damage making the drive home. We had a brand new subaru that went into limp mode, turned out to be gas with very high ethanol content, subaru dealership in South Carolina took all the fuel out of the tank and put a little fresh fuel in. After a short while driving with good fuel, and a few clean engine starts, the CEL went out and limp mode deactivated.
Had it been different codes, that WOULD have been proper motivation. :thumb:
 
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