Can someone help me out with the o2 sensor? My car is stating I have a P0420 (cat below efficiency threshold) and I'm close to 100k miles. I feel like my o2 sensor is potentially failing because of its intermittent behavior, but I could be saying that to replace the cheap component instead of the cat (and because California only allows an OEM replacement).
No smell of sulfur, gross pollution or struggling performance as of yet. This morning when my CEL went away, I noticed a lack of performance putting my throttle plate around 60-ish+ % before the CEL came back on.
you might THINK the o2 sensor is gonna be cheap but you may be wrong. that being said it looks like you may be right
Xavier Garcia
It's at a relatively easy area to remove and reinstall. So the part price would be the main issue (100-400 dollars depending buying from the dealer vs finding online).
It's still way cheaper than the CAT if I can get some reinforcement that my logic is ok to assume the sensor.
Cooper Morales
Get the cheapest noname replacement you can find. Rear O2 sensors are no big deal.
But first see if you can get the old one out. That can be a real bitch and make you think you should double-check that it might not be something different or if it'd be easier to buy a new cat to go with your new sensor just in case.
Bentley Gray
Oh also do you have a graph of the front O2 sensor to line up against that? That reading just looks fundamentally flaky, but if you're feeling doubtful then you might want to make sure that the reading from the front sensor looks like the ECU is trying to be sane and the reading from the rear is obviously just whacked out.
Alexander Morris
I'm constantly weary when trying to use the turbo XTs AF sensor because everyone claims it's a shitty wideband, but from the looks of it currently; the sensor has seemed to be relatively consistent compared to the rear o2 sensor.
Elijah Ward
Not XT, forester* Excuse the retardation.
Joseph Edwards
Yeah that does look pretty good (and yeah the older widebands they used in and around those Foresters aren't great compared to the fancy new ones, but they're good enough for the intended purpose).
I assume of course this is with the car good and warm so it's running closed-loop. It appears to be based on the way it's trying to flick the reading back and forth. And the rear doesn't look too terrible, so I guess I can't say I'm surprised the P0240 would have gone away. That makes me tempted to say just leave the sensors and the cat alone for now to see how things develop.
If you notice a lack of performance when you put your foot into it, that makes me wonder if you're feeling the transition from closed-loop to open-loop where the engine is no longer using the O2 sensors. If that's what you're feeling then I would start to wonder if your MAF is getting old and the ECU is having trouble learning good fuel trims. Here again, I would expect you to start getting different codes, so if I were in your position I would give it some time to see if anything else shows up before throwing money at it.
Connor Morales
You're spot on in regards towards the car already being warm. I'm not entirely sure why the P0420 has gone away either, but the last time it showed up was a few months ago.
I might have been feeling the CL/OL transition and I wouldn't mind showing some of the latest data from the MAF. The LTFT at idle is kinda high from where I'm standing, but the mechanic I took it to said it was fine :/
Logan Parker
Here is the LTFT with RPM as the horizontal axis
Aaron Powell
That curve looks consistent with the O2 readings.
Whether it's the MAF or the cat or the O2 sensor, my guess is that it's only just starting to get wonky enough for the ECU to have trouble figuring out what to do.
Jonathan Walker
I was gonna post the MAF (G/S) with RPM. Here it is right here
Isaiah Clark
Oh shit have all of these been RPM horizontal? I just assumed that was time in seconds or something.
Anyway, as far as LTFT goes, that's one where if it starts to bang around high to low over longer periods of time for no obvious reason then that's a hint the ECU is operating too far off the base maps to figure out what's going on.
I forget how steady short term trim is supposed to hold if everything is alright, but it will tend to track front O2 more obviously in terms of how quickly it can change.
Joshua Martin
might wanna sort the data by engine speed in ascending order
Jose Murphy
MAF is tough to judge from readings alone unless it's clearly busted. It can just start reading off from being old or dirty, or maybe reading more off at low flow vs. high flow, and then the ECU starts having trouble getting the fuel trims right because it doesn't approximate the pre-programmed maps.
If this is the case, you might expect to start feeling / hearing the engine stumble or skip a beat from leaning out to much. Or you might start getting misfire codes. Or both.
Levi Cruz
A few of them are because I feel like it's easier for me to read personally.
I can ascend some of them, but excel makes it hard to read a couple of them (for me anyway).
When you say "stumble" or "skip a beat," would a terrible enactment example such as this kinda be what you're referring to:
It's hard to tell from that description if you're just talking about typical subaru exhaust rumble with the occasional pip pop bomp from a bit of unburnt fuel hitting a hot cat (or whatever it is that does a good impression of sounding like that when it's idling at a red light)
If it's just starting to lean out then it would be more like skipping an occasional beat at first, not something constant. Only after it gets bad enough that the car starts to bog and not respond when you try to give it more throttle, or threatens to stall out on you would you expect it to misfire repeatedly.
Daniel Lewis
ahhhh, nvm then. Your first sentence is what I was thinking of. I just didn't have a good way to describe it because this is my first H4.
I haven't had it threaten to stall or bog out on me. Closest thing I can think of is I had a coolant line rupture and this code start creeping on me after I replaced the coolant lines and did a flush.
Aiden Ward
It could just be that the sensor or the cat is starting to get old. It wouldn't hurt to clean the MAF if you want but otherwise, like I said, if it were mine I'd let it go and wait for more clues.
Jason Anderson
Not sure if the state you live in does yearly inspections (by caring I'm guess you do live in such a state)
But have you thought about/tried doing a sensor spacer to see if that solves your issue? Or, at least gives you an understanding of the overall issue.
Alright. I don't need to necessarily rush it and my car is doing well otherwise. I appreciate the input and advice!
Aiden Rogers
I live in the most notorious smog state in the 50 states (California). My bi-yearly smog is around the corner-ish, but when I reset my codes, the P0420 doesn't show up for approx. 200+ish miles. So it's been a very strange scenario for me because I've taken it into a shop and the dealership with no one wanting to pull the trigger as to what the issue may be.
Austin Hall
You have to get it smogged TWICE a year? Jesus Christ what bullshit. Yeah if it reliably takes that long to throw a code just clear it and drive around a while first or whatever it is you need to do to slide by the tests.
Should be somewhat comforting at least that everybody you've asked so far agrees that it's not obvious that you should be throwing money at anything in particular at this point.
Hunter Rogers
No no, once every two years is what I meant to say. Sorry if bi-yearly didn't make sense (it did in my head). I just wish I didn't have the problem because I'm very uncomfortable with no answers and I don't have the resources to be a parts cannon.
Nathaniel Anderson
checked and nothing about a P0420 is anything to worry about except for passing an emissions check, so at least you're in the clear as far as worrying that something important might be about to break. Just watch for any developing patterns, which it seems you're not having any trouble doing as it is.
Lucas Wilson
>Sorry if bi-yearly didn't make sense (it did in my head)
Getting paid bi-weekly works the same way.
English is fucking weird and I'm no trained specialist at it. (I wanna be employed)
Luke Cook
I think I've reached the point of paranoid, but thanks for letting me know that I shouldn't be as ridiculous as I may have been. I've been logging to and from work, school and any trips I make in-between to try and see if something will eventually come up.
I personally hate English myself with all the different ways things can be said, but the employment will happen user!
Daniel Cook
>but the employment will happen user!
That's why I study engineering :P
Kayden Long
If y'all don't want to change your O2 or suspect it's not the sensor, just dump a gallon of acetone from Home Depot in your half tank and drive in 4th gear or high RPM on a freeway run. Cleans your cat.
If you worry about corrosion, don't be a bitch. It's 1 gallon.
Connor Lee
>Things I will not attempt at all.
Jayden Gutierrez
What? Are you afraid to try the scotty kilmer special?
I bet you like mercedes too.
Samuel Allen
Mercedes is way out of my price range, so I'm pretty indifferent towards the brand.
Ryan Scott
senpai, I think you don't understand the meme
(that retard telling you dump acetone in your car is not the meme but kilmer spouts it)
