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Discussion Starter #1
Hi All
Decided the time was right to change my o2 sensors as I am at 150,000 kms which according to NTK is the end of the serviceable life of the sensors in the X trail. Never had a check engine code or performance issues. Nevertheless, like spark plugs they do suffer performance degradation over time and in addition to affecting gas mileage, a bad one can lead to an early death for your catalytic converter. That said, I note that nowhere does Nissan specify a change interval for them. So I am curious how many owners actually replace them before things go bad, or do most just figure on waiting until ecu throws up an error code?

Anyway I am happy to say that I got the upstream one changed, however the downstream sensor is proving difficult. Had to give up on it and hope power blaster over a few days will help on a later attempt. Nevertheless the upstream is the more key of the two, and changing it has resulted in a minor performance gain. I will have to monitor over the next few weeks to see what happens with gas mileage.
So my question is should I just leave well enough alone and just wait for the downstream sensor to fail? Or do I suck it up, and find a way to get the old one out even it means breaking it off to get a full 22mm socket onto it?

PS for anybody doing this, getting the sensor connectors off the metal tabs they mount to can be very challenging. Patience and determination are required.>:D
 

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Discussion Starter #2
Well PB Blaster was of limited help for the downstream sensor. Finally I stripped it so bad, I broke off the end, and then got to force a 7/8 ratchet head onto it, and miracle of miracles it came loose and out. The actual install of these is easy, its getting them out that is the headache. Will keep on eye on gas mileage but so far engine seems very happy with this change. Its like a mini tune up.
So, I am happy, and I know its done.
 

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When installing the O2 sensor, it's recommended to apply anti-seize compound to the threads. This way any future replacements should be much easier to do.
 

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Discussion Starter #5
Hi Otomodo and Rogoman
Never got around to using a torch. Would be another way to go, but not my preference. Problem with downstream bottom one is getting the o2 sensor socket on it properly. I kept thinking I was getting it loose and instead I was just stripping the bolt. Couldn't get proper grip. Ended up breaking off the top and getting a full socket on it. With my pipe extension was able to bust the rust seal and get it screwed out. New one went in smoothly.
And Otomodo you are right about anti seize. I wonder if Nissan put any on. Was happy the NTK's came with some pre-applied. Didn't overly tighten them as specs are something like only 30 lbs. I may take them out again in a year or two for examination, but otherwise they should be good for a good many years. The old ones showed very minor silicone staining upstream, and a wee bit of carbon on bottom of downstream one, but otherwise other than being gray and older, looked good. They were still functional and not setting off any codes.
Great news is that with a few more drives under my belt including some highway, its all positive. Bit like putting on new rubber, or having your tennis racket restrung, There is this bit of incremental goodness that you can feel. Seems to be getting a bit better gas mileage too. Idling really nicely as well.
All told I am glad I did it. Hope it pays off with a longer lived cat, and an engine that keeps performing great. My guess is that most the X trails in Canada,given their age, would benefit from new O2 sensors. I was actually surprised that there is not much info or discussion about them here in the forum.
 

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Hi X-TRAILERS, As a newcomer, and having just bought a 2007/8 GX 2.5 petrol version here in Brazil, I'm not sure about the sensors you've been threading about. What I do know is that, soon after acquisition, the engine warning light came on, and, after a few kilometres, cut out. Luckily, I could restart and make it home. My competent mechanic, 2nd generation of a Japanese immigrant family, flashed his "videogame", his electronic test equipment. It showed a rev (rpm) sensor hidden at the back of the engine needed replacement. VERY EXPENSIVE ! Next day, I noticed that the idle would keep rising and falling between 1,500 and 2,000 rpm. Strangely, upon turning on the airconditioner (AC), the idle would fall to 800 or so, i.e the normal revs when the AC is off. Well, my Jap wizard used his electronic device again, and with a little reconfiguration, consisting of turning the ignition on and off at certain intervals, managed to fix the problem. It also goes to show that you don't need to pay an even more expensive arm and a leg at an authorised Nissan dealership. Good X-ing. BRIAN
 

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As Quad knows, I had the upstream one done, and then the idiot light came back on, with the Minute Muffler guy diagnosing it as the downstream sensor, better get it replaced or your cat will go, yadayada...Spoke to another mechanic (a private guy) who advised me to not bother right now if everything runs fine and my mileage is good. it did improve after the upstream one was replaced but I will NOT go back to MMuffler as I have since learned they just like to upsell and milk you for as much as possible...:(
I have been getting about 8.5/100km...
 

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Discussion Starter #8
Molly you may have had some problems but you do get great gas mileage. Its rare I do better than 12, but then its mainly city driving with rush hour traffic. Re the downstream oxygen sensor, it appears that its principal role is simply reporting that your cat is functinonning normally. Unlike the upstream one its not key in allowing your ecm to regulate your optimal fuel trim. That said its job might not be purely passive. However I cannot find much info on it. Nevertheless, probably worth it to change it out for piece of mind and to turn the check engine light off.
 

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Thanks, Quad. I do mainly highway driving and rarely speed, so that likely helps. I will eventually get the other sensor done when the budget allows...I will use this guy who just got rid of that strut noise. I trust him! Yay!
 

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I m keeping an eye on this thread to see if you get better fuel economy.
My wife can t do better than 13l/100km and she s working 4,5km from home but a lot of stop signs on the way.
At first i tought it was the spark plugs,it s been done and no big difference.
Know i was thinking about the o2 sensor and you tell me 12l/100km is your best.
 

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Discussion Starter #11
Well Otomodo if its any consolation my worst was 14.6L. You might also keep in mind the revised transport Canada figures which put the x trail at 9.6 Hwy and 12.2 City. Awd versions get worse mileage than 2wd ones. Lots of things affect gas mileage, the o2 sensor is just one part of the mix. My point is that they are a wear item that can degrade by something like 25% of their original performance before the ecu reads them as bad. I don't expect any miracles in the mileage dept, maybe a 2.5 to 5% increase. All I can tell you is that the engine likes the change. Its running really smoothly.
 

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Discussion Starter #13
I used Lucas upper cylinder and injector cleaner a month prior to the change. I do it once or twice a year. Do not have any problems I am aware of with my injectors. My gas is mainly purchased at the local Esso or PetroCan , tends to be high quality. I have no fears for my fuel filter. Any problems with yours???
 

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Two years ago the xtrail was feeling slow and the overdrive didn t engage as usual and when engaged it would disengage by a simple feather touch on accelerator.
It felt better after a spark plug change then 6 months later it came back.
I ve used 3 bottles of injector cleanner on a 3 month period with no result. A trusted mechanic told me that it can be used to prevent injector dirt but not to clean a dirt injector.

The worst part of it is the fuel gage is now inaccurate,when there s 20l of fuel in the tank it tells me there is 3/4 full.
Oh my,Oh my!!!!!

Manda pá grota ;)
 

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Discussion Starter #15
Otomodo I am having a hard time following your logic. Sounds like you should have changed transmission fluid two years ago. Injector cleaner has rather limited benefits, and too much and too often can cause problems. Its a pain that your fuel gauge isn't working properly but I think its a completely separate issue. Did you ever do a drain and fill of your tranny?
 

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Discussion Starter #17
Hi Otomodo, for what its worth there has been an improvement in gas mileage. Its hard to be super exact as weather has an impact, not to mention traffic conditions. But based upon my last 4 fill ups I would say its getting 30 km to 50 km more per tank. Engine is really smooth and no vibrations at idle. After 8 years and 150,000 kms I think the old ones qualified as worn even though not to the point of setting off a code. My thinking is a cleaner burning engine is not only good for the environment, its also good for your car if you want it to last a fair bit longer.
 

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When i had the obd2 Bluetooth device connected to the xtrail, this is one of the options i could see on a smartphone.
I ve posted it to see if it was possible to share from a smartphone (autoguide app).
Now that it works here is the o2 voltage i was getting from the 2 gauges available (active with the app (2/7) ).
http://1drv.ms/1VaKop8 first gauge moving from 0,3 to 0,8 non stop the second moving from 0,4 to 0,6 slower.
The app name is Torque free
 
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