about to do F/A sensors

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about to do F/A sensors

Postby disallow » Sun Apr 10, 2011 9:12 pm

Hey all,

So I went to the local surplus tool store (princess auto) and purchased 2 o2 sensor sockets as well as a thread chaser.

Any pointers for me before I take a crack at replacing the primary o2 sensors (also called Fuel/Air Sensors) tomorrow?

t


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Re: about to do F/A sensors

Postby Npath » Mon Apr 11, 2011 2:36 pm

disallow wrote:Hey all,

So I went to the local surplus tool store (princess auto) and purchased 2 o2 sensor sockets as well as a thread chaser.

Any pointers for me before I take a crack at replacing the primary o2 sensors (also called Fuel/Air Sensors) tomorrow?

t
Drive it onto some ramps, so you get more space. Also, spray the threads with WD-40 or equivalent and let it soak. I don't know if the OEM have anti-sieze coating on them or not. If it's super tight, loosen and tighten so it breaks all the carbon off and again, lube it.

How's your mileage? I've noticed increase in mileage when the weather warmed up. 18.5L/100km currently.

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Postby Tech » Mon Apr 11, 2011 4:24 pm

why you replacing?

I'd go from the wheel well. Take the front wheels off and go from the inner fender liner. You can bend it or remove it. The connectors also clip into little metal tabs. Unlock the grey tabs FIRST, or if the tab breaks, the connector wont stay secure. The sensor won't be hard to get out, after the first crack, the should spin out pretty easy. On one hand it helps if its warm, but on the other, if you haven't done them before, you run the risk of burning yourself....

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Postby volvite » Mon Apr 11, 2011 8:08 pm

You would be better off to use PB blaster (Parts Breaker) than WD-40. It's more of rust breaker than WD-40 is.

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Postby disallow » Mon Apr 11, 2011 8:37 pm

Tech wrote:why you replacing?

I'd go from the wheel well. Take the front wheels off and go from the inner fender liner. You can bend it or remove it. The connectors also clip into little metal tabs. Unlock the grey tabs FIRST, or if the tab breaks, the connector wont stay secure. The sensor won't be hard to get out, after the first crack, the should spin out pretty easy. On one hand it helps if its warm, but on the other, if you haven't done them before, you run the risk of burning yourself....
I read the voltages off of my Superchips tuner, and they are reading lean. I can definitely tell that the truck is not running lean (exhaust smells of unburned fuel before cats heat up), and I am experiencing poor fuel economy. I do not have any CEL or codes.

Thanks for the pointers. Decided not to do it tonight as I am feeling under the weather.

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Postby volvite » Mon Apr 11, 2011 8:43 pm

What engine do you have?

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Postby disallow » Mon Apr 11, 2011 8:55 pm

volvite wrote:What engine do you have?
v6. no v8 in 05.

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Postby Tech » Mon Apr 11, 2011 10:22 pm

Those trucks are known to be smelly after cold start. Keep in mind that the voltages for A/F sensors are not the same as O2. I've yet to replace an A/F sensor in a Pathfinder for anything other than physical damage. Feel better!

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Postby disallow » Wed Apr 13, 2011 7:00 am

Tech wrote:Those trucks are known to be smelly after cold start. Keep in mind that the voltages for A/F sensors are not the same as O2. I've yet to replace an A/F sensor in a Pathfinder for anything other than physical damage. Feel better!
What is the normal voltage I'm supposed to be seeing? Are they supposed to be different on Bank 1 and Bank 2? Per my earlier posts, I get 0.3v on bank 1, and 0.6v on bank 2. To me, this points to an issue with the way the sensor is reading.

I would assert that O2 sensors are one of those items that tends to be left alone at service shops, probably because they can become lazy and nonfunctional without throwing a code. Without the code to backup why certain work is being performed, the service shop has no data to show the customer, and opens themselves up to accusations of doing unneccessary work.

But its a fact, O2 sensors get old, and lazy. So we'll find out whether my theory holds true.

I had a 98 civic with about 250k kms on it a few years ago. It was getting to the point where it was only achieving 25-28mpg, when as new it would get about 35-40mpg. Replaced the primary O2 sensor, and mileage immediately jumped. No codes thrown.

One of the old threads I've discussed the O2 sensors on:

http://www.thenissanpath.com/viewtopic. ... ght=#31532


t

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Postby Captain » Wed Apr 13, 2011 8:58 am

I watch your videos of you showing the readings. I would sudjest cleaning your fuel injection system first before changing parts out. Reason Im sayting this. If you have a weak/cloged injector on bank 1 it will show leaner numbers on that side, even though the emc is increasing fuel parameters for that side. Your sensor might be showing you the correct readings. Most of the time when a sensor is going out it reads waky numbers out of the norm then goes back to normal readings till it finally breaks.

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Postby disallow » Wed Apr 13, 2011 6:16 pm

Captain Smoke Eater wrote:I watch your videos of you showing the readings. I would sudjest cleaning your fuel injection system first before changing parts out. Reason Im sayting this. If you have a weak/cloged injector on bank 1 it will show leaner numbers on that side, even though the emc is increasing fuel parameters for that side. Your sensor might be showing you the correct readings. Most of the time when a sensor is going out it reads waky numbers out of the norm then goes back to normal readings till it finally breaks.
I agree. And the voltage readings are pretty stable. Its the trim values that are wacked. Without a proper baseline, I really don't know what they are supposed to read, but they are really all over the place.

In any case, I have the sensors already. I'll take one for the team and see what the results, if any, are.

Does anyone have any data or info they want me to gather before I change them? I have my most recent fuel economy numbers, and videos of the sensor outputs. Anything else?

T

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Postby disallow » Tue Jul 26, 2011 10:18 pm

OK guys,

I finally got around to doing these pain is the butt sensors. Total job took me about 2 hours, each side has its own unique set of issues. I took some pics of the sensors old vs new, I'll put that at the end of the post.

Started with the passenger side. Jacked vehicle up, removed tire. Unclipped the fender well and pulled it back as far as I could. Used some bungy cords to hold it back in place. From this angle you have a straight shot to the sensor through the wheel well. The plug is a little more challenging, but not so bad. The reason this side took so long is that I didn't know what type of connector was being used, so I didn't want to break anything. But its a very simple connector, the female end is on the body side, and it has a clip that swivels up. Once its swiveled up, the plug comes apart very easily. There are 2 mounting points on this side, both easy to find. The plug base is very hard to get at, so I ended up breaking the plug off of the mounting point and removing the clip with a flat head screwdriver. Made it very easy to put the new sensor in.

Getting the old sensor to break free was no big deal. Engine was cold. Used a 3/8" ratchet with a small pipe extension, along with an O2 sensor tool acquired from the local surplus store (Princess Auto for you Canadians). I used the thread chaser to ensure the threads were clean, and then threaded the new sensor in. This side took about an hour and a half (30 minutes spent scratching my head with regards to the connector.)

Driver's side was a little different. Pulled the fender well back again, with tire removed. Access is better for the plug end, which is done from above in the engine bay. There is only the plug mount on this side, no intermediate mount. Access to loosen the sensor was decent, but threading in the new one was harder due to access. This side took about 30 minutes.

Anyways, let me know if there are any questions.

Here are the pics of the old vs new sensors:

Image
Old on left, new on right

Image
Old vs New sensor end of the plug

Image
Old (broken) vs New plug end compare

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Postby volvite » Tue Jul 26, 2011 10:31 pm

Nice write up. The pictures describe alot too.

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Postby found » Wed Jul 27, 2011 8:59 am

here is how you test the a/f sensor as well as voltage you requested.


1.) Start engine and warm it up to the normal operating temperature.
2.) Turn ignition switch OFF and wait at least 10 seconds.
3.) Start engine and keep the engine speed between 3,500 and 4,000 rpm for at least 1 minute under no load.
4.) Let engine idle for 1 minute.
5.) Set voltmeter probes between ECM terminal 74 [HO2S2 (B1) signal] or 55 [HO2S2 (B2) signal] and ground.

6.) Check the voltage when revving up to 4,000 rpm under no load at least 10 times. (Depress and release accelerator pedal as soon as possible.)
The voltage should be above 0.68 V at least once during this procedure.
If the voltage is above 0.68 V at step 6, step 7 is not necessary.


7.) Keep vehicle at idling for 10 minutes , then check voltage. Or check the voltage when coasting from 80 km/h (50 MPH) in D position. The voltage should be below 0.18 V at least once during this procedure.
If NG, replace heated oxygen sensor 2.

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Check resistance between terminals 3 and 4.

Resistance: 2.3 - 4.3 Ohms at 25 °C (77 °F)

Check continuity between terminals 3 and 1, 2, 5, 6, terminals 4 and 1, 2, 5, 6.

Continuity should not exist.

If NG, replace the air fuel ratio (A/F) sensor 1.


I hope that helps :-)

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Postby disallow » Mon Aug 08, 2011 8:26 pm

Just an update on this:

The performance of the truck has changed quite a bit, for the better. Mileage has also improved. I'm only on tank #2, but the Avg fuel economy is much better, closer to 10-12L/100km. Before we were at between 14-16L/100km.

I towed my camper with the truck this past weekend. At one point I had to look back to see if the camper was even there. Acceleration was awesome, fuel economy was much improved under heavy load.

Will continue to monitor.

t


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