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Discussion Starter · #1 ·
Sup guys

I've been looking at my fuel mixture for a while now and felt like it was just off, Here's what I see. (Please correct me if i am wrong)



Observation 1
A lot of what I've read and researched, say that the O2 sensor is to poll between 0 - 1 volt rapidly. I've never seen my 02 sensors do that and I am thinking that maybe this is a newfangled sensor that is being used, And may be different that traditional sensors. (Or just plain lazy?)

Observation 2
My bank 1 and bank 2 sensors are not even close to each other. bank 1 is always below .5v and bank 2 is always just above .5. I am thinking that there is something going on in bank 1. (Maybe lazy at lean and causes bank 2 to richen)

Observation 3
When I gas it, downstream sensors rise. Meaning upstream cats are pretty much done? as downstream would be pretty steady meaning that cats are doing their job.

Am I completely off?
Would love you hear what you guys think.
 

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the old narrowband sensors could really only tell if the mixture was leaner or richer than stoich, so the ecu would try to flip back and forth between them. the new wideband sensors allow the ecu to hold the mixture where it wants in a given steady state.

do you have any data showing the engine under load? i thought the wideband O2s used a larger voltage scale than the narrowband ones. i have a feeling that your apparent wide discrepancy between banks might be a function of a too-narrow range on the chart. you should be able to force them to show full lean at least by running up and doing a coast down, which should shut off the injectors.


EDIT: also what are the operating conditions this data was taken in? cold start? warm restart? just warmed it up and drove around the block?
 

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Discussion Starter · #3 · (Edited)
Hi Strizzo,
Thanks for the explanation of the wide vs narrow band sensors. Helped me understand.

The graph was not taken under much load. Truck was warmed up, parked it for about 1/2 hour. Hopped back it and took it for a drive. Engine temp was just a little below operating temp when I began logging the data.

This data was taken for 10 minutes.
First 3 minutes was a short drive, 2 minutes idling, and 5 minutes after that, hitting the gas and back down.

I gathered this data with the torque android app and it logs the sensor data every second.

This evening after work I can upload another under load with fast acceleration, and see if they move.

btw I have an 06 S with ~130k miles

Edit:

I read up on Wikipedia and say this regarding my first point.

The ECM is constantly monitoring the pump cell current circuitry, which it always tries to keep at a set voltage. For this reason, the techniques used to test and diagnose the regular Zirconium O2 sensor can not be used to test the wide-band AFR sensor. These sensors are current devices and do not have a cycling voltage waveform.
Thanks again.

Now have to figure out these readings. If anyone has their graphs, please feel free to post for comparison.
 

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I have a feeling you'll run into sensor sample rate issues if you try to log too much, but try and get some data logging throttle position, rpm, and just the upstream O2 sensors. the downstream after-cat sensors are mainly so the computer knows how well your catalysts are working, so you could drop them off the list if you need to monitor more sensors.
 

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Discussion Starter · #5 ·
Good Idea I'll add those PID's to the list for a better analysis.

According to the Service manual, Upstream Sensors should be at 1.5v when holding at 2000 RPM, weird that I am no where even close to 1v.



In addition to this they provide steps to test 02 sensor.

Overall Function Check
Use this procedure to check the overall function of the air fuel ratio (A/F) sensor 1 circuit. During this check, a
1st trip DTC might not be confirmed.
WITH GST
1. Start engine and warm it up to normal operating temperature.
2. Drive the vehicle at a speed of 80 km/h (50 MPH) for a few minutes in the suitable gear position.
3. Set D position with “OD” OFF (A/T) or 5th position (M/T), then release the accelerator pedal fully until the
vehicle speed decreases to 50 km/h (30 MPH).
NOTE:
Never apply brake during releasing the accelerator pedal.
4. Repeat steps 2 to 3 for five times.
5. Stop the vehicle and turn ignition switch OFF.
6. Wait at least 10 seconds and restart engine.
7. Repeat steps 2 to 3 for five times.
8. Stop the vehicle and connect GST to the vehicle.
9. Make sure that no DTC is displayed.
If the DTC is displayed, go to EC-235, "Diagnostic Procedure" .
 

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My thread on Cipher (UpRev's diagnostic tool) may help: http://www.thenewx.org/forum/showthread.php?t=55943&page=2

The torque android app is great for getting raw data, but without a formula to convert it its hard to tell whether or not voltage readings are correct when relating to AF mixture.

Cipher is about $200 from UpRev and the company has gone through the legwork to determine proper readings / conversions off Nissan sensors. Plus should you decide to have them tune it, they can.

Lastly, you could check out the AFR ratio reading. Most engine monitors have this built in (I know my Ultragauge does, as does Scangauge, I'm assuming the torque app should).

AFR ratios in the 0.85 to 0.90 range are typically where you want to be. Or you might have an option for "AFR Commanded Value" which shows a percentage. The closer to 100% (98 to 102) the better.
 

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Discussion Starter · #7 ·
Ah. I see what you are saying klundquist. Perhaps, formula for O2 values do not take into account wideband voltage. I shall do more research.
 

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Here's my two Charts. One is my ride home with lots of stop and go. The second is a more freeway ride. Both charts are from Engine ON to OFF, so full warmup cycle. Interesting to see that with highway driving the 2nd O2 sensors never registered voltage, BUT for stop and go they were all over the place after heating up 10 minutes into the ride. Weird that 1 Bank runs Richer than the other bank.

Hope this works! Trying to do from work which blocks most photo sites.



 
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