# DYI steps please - 97 Pathfinder Oxygen Sensor and Throtle Position Sensor



## elmasto (Aug 19, 2008)

Hello folks,
I have been getting a terrible gas millage on my 97 Pathfinder (12 MPG city), so I want do some maintainance. I am planning on replacing the plugs, front oxygen sensors and throtle position sensor (Which I know is bad). Alas, I have never done those, and would like to know.

So, can any of you nice folks point me to a step by step instruction on how to change my oxygen sensors, and if it is DYI-able, the throtle position sensors? Otherwise, what is a fair rate at the mechanic? (Autozone price O2 sensor - 60, TPS - 85).

Thanks,


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## underling (Nov 26, 2006)

o2 sensor (depending on which one you are replacing) will be right on the exhaust pre and post cat. go to your local auto tool supplier and buy an o2 sensor socket. i changed the 2 rears in my '98 in about 1/2 hour from start to finish. Fronts look a little trickier but still doable. just need a couple extensions. Also to break the one side free on the rear o2's I used a 12" breaker bar on my ratchet. and just gentle steady pressure broke it free.

How do you know your TPS is bad? error code?


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## NPath (Dec 12, 2004)

underling said:


> o2 sensor (depending on which one you are replacing) will be right on the exhaust pre and post cat. go to your local auto tool supplier and buy an o2 sensor socket. i changed the 2 rears in my '98 in about 1/2 hour from start to finish. Fronts look a little trickier but still doable. just need a couple extensions. Also to break the one side free on the rear o2's I used a 12" breaker bar on my ratchet. and just gentle steady pressure broke it free.
> 
> How do you know your TPS is bad? error code?


If I may add, use WD-40 or equivalent on the O2 sensors before and during the removal process. It should help if you let the lubricant set in a little before actual removal. 

I don't know if the spark plugs have a cover on them attached to the cable. But, before removing the spark plugs, get a screwdriver and loosen up the sand and crap trapped at the base of the spark plugs, then blow it out with compressed air or canned air, one at a time. Last thing you need is crap getting into the combustion chamber. Did it on my 95 Pathfinder and glad I did, lots of sand.


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## elmasto (Aug 19, 2008)

Thanks for the replies.
Changing the spark plugs went alright except the last one at the back of the engine which was a bit hard to reach.
I read in the Chilton manual (which I borrowed from the library, did not know they kept those till yesterday) that the pre-cat oxygen sensors are the ones used to determine the fuel-air mixtures, hence why I wanted to change them. @underling: you are right. I can see the front O2 sensors (in the hood) and especially the driver side seems tricky to get to. Has anybody tried to change the pre-cats that themselves?

The TPS is from an error code (Actually two codes with same explanation). I have ordered the parts for that as well. Will see how that goes and report.


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## underling (Nov 26, 2006)

seems i suffer from the same problems as you, and many others with the low fuel economy...at least in part mine can be attributed to a heavy foot. I don't believe (or at least can't train myself) to lighten up my foot on acceleration. I have taken most of the same steps. Replaced the plugs and wires, replaced the air filter and fuel filter. Replaced the rear o2 sensors and still have to do the fronts. I want to attempt cleaning the MAF sensor as well but am a little scared of damaging it. Also, I am going to do the distributor cap/rotor, which i have heard is good to do when the plugs/wires are done.


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## elmasto (Aug 19, 2008)

Report:
I changed the spark plugs and the air filter a couple days ago. 
I changed the Throttle Position Sensor myself (because of a code), which seemed fairly easy to do, and is plainly accessible. Adjusting it might be a bit tricky. I hope I have got it right.
I changed the front two oxygen sensors. I bought the parts from Murray's Auto Parts, which matched Autozone's price and gave me 5% on top of that. I took them to my mechanic which charged me for an hour worth of labor. The front two are indeed tricky and hard to reach, so I am glad I took it to the shop.
I filled up my tank this morning, and am waiting to see if there is any improvement.
Thanks for your help.


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## underling (Nov 26, 2006)

update with whether or not there was an improvement as i still have to do my fronts. I am curious as to whether you would see a significant difference.


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## elmasto (Aug 19, 2008)

Report 1:
I drove my first 80 miles (entirely city driving, with stop and go) after the maintainaces above (and a 33 psi tire adjustment). My milage now is ~15 (14.83 MPG to be exact). That is about a 34% improvment from the previous 11 or 12 I got with it. I will report on mostly highway driving later.


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## simplegame (Aug 2, 2015)

do the post-cat oxygen sensors effect mpg....or just the pre-cat?


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## billhappy (Jun 14, 2015)

*NTB99-053b/Revised TPS Adjustment*

Hello To all,

AS far as the TPS part of your post I would suggest reviewing this revised adjustment bulliten. I'm not sure if this is the place or way to post new related question, I tried following the instruction to use .012 feeler gauge . What I encountered is the space between the throttle drum and throttle drum idle stop is about .045 cold about .028 thousandths warm. Rotating the tps to get appropriate ohms reading was also to no avail. I did everything I could to get cold throttle drum position to change by trying to adjust fast idle cam directly below. Also to no avail. 

PS. I should have said this a 97 pathfinder se I've been working. 

I am awaiting arrival of new tps , question is how to adjust in light of throttle drum measurement space being so large ? 

Any and all comments would be greatly appreciated


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