SCT data logging question. Testing the cats.

[hades_1]

I was trying to test my cats (96 Cobra) as I did notice some loss of power and a quieter engine and/or exhausts in recent weeks.

I got a varying voltage on both the front sensors that go from ~.01 to .9; and at the rear they start around ~0 while idling, and then bank 1 gets to a steady ~0.6 while driving, but bank 2 is still around 0-0.1; after a WOT things change and bank 1 is now going from 0.6 to 0.8 (driving normally after the WOT) and bank 2 is 0.7 to 0.9.
That doesn't look normal to me... but I am not sure what that means exactly.




(blue graph is RPMs)

.Csv file located here:

http://www.mediafire.com/download/3ace4k6malpa19x/datalog3_stocktune_3-06-13.csv

Does that make any sense?
Any help greatly appreciated!

 

[hades_1]

Updated original post with better info, pictures and data log. Thx!

 

[watman02]

the fronts should be switching as it looks like they are. the rears should be running near the same voltage as each other and should not change much at a steady state if the cats are working correctly. usually if the cats have failed the will be mirroring the front o2 sensor. and this will set a cat efficancy fault code. have you looked for a exhaust leak?

 

[hades_1]

I have not looked for an exhaust leak, no. Less than 6 months ago, I did have some, but I brought it to a muffler shop to have them fix it. There could be some new ones since, I guess :<
I should check that out!

It doesn't look like my rear o2 sensors are mirroring the front o2 ones, the rear are still relatively steady unlike the front but both rear o2 sensors aren't equal in terms of voltage, and the voltage can get higher than what it should be (0.6-0.9 instead of a steady 0.5-0.6V I believe).

 

[006]

Your bank 1 upstream O2 sensor is "lazy". It's not switching like the bank 2 upstream sensor. The spikes should almost mirror each other.

It could be fouled up or gone bad.

Both your rear downstream O2 sensors are switching like they should.

 

[hades_1]

Your bank 1 upstream O2 sensor is "lazy". It's not switching like the bank 2 upstream sensor. The spikes should almost mirror each other.

It could be fouled up or gone bad.

Both your rear downstream O2 sensors are switching like they should.

Actually both front O2 sensors are almost identical, I am having troubles with Live Link to put them on the same scale sometimes. Not sure why. But yeah, they are almost identical going from 0.1 to 0.9 in a wavey pattern matching the STFTs patterns.

My concerns are more toward the rear O2, where the bank 2 sensor doesn't read *anything* until after a WOT at ~3mins on that data log. After that WOT, both rear sensors are steady but they are steady at a rather high voltage of 0.6-0.9V; which I believe is too high (shouldn't they be around 0.5V?)?

Anyone has a data log of working O2 sensors I could have a look at?

Still trying to figure out what could have caused my car to become quieter over time...and plugged cats seems to be the only thing that I can think of that makes sense (an exhaust leak should make it noisier).

 

[006]

Actually both front O2 sensors are almost identical, I am having troubles with Live Link to put them on the same scale sometimes. Not sure why. But yeah, they are almost identical going from 0.1 to 0.9 in a wavey pattern matching the STFTs patterns.

My concerns are more toward the rear O2, where the bank 2 sensor doesn't read *anything* until after a WOT at ~3mins on that data log. After that WOT, both rear sensors are steady but they are steady at a rather high voltage of 0.6-0.9V; which I believe is too high (shouldn't they be around 0.5V?)?

Anyone has a data log of working O2 sensors I could have a look at?

Still trying to figure out what could have caused my car to become quieter over time...and plugged cats seems to be the only thing that I can think of that makes sense (an exhaust leak should make it noisier).

Hmm, why do your graphs above show your bank 1 upstream O2 sensor flatlining? This would indicate that it's not switching as it should.

Here is a datalog of mine from these threads:

http://www.svtperformance.com/forums/new-edge-cobras-51/936712-asking-some-return-help.html

http://www.svtperformance.com/forums/tuning-la-carte-375/937117-help-datalog-reading.html


Lazy O2 in pink

Replacement/new O2 in pink:

Rear O2's switching normally:

You can see that my two issues were the EGR (flatlining) and the bad/lazy O2 sensor on bank 2 (slow waves/not switching at the same rate as the other side).

 

[hades_1]

Thanks for the data logs. Looks like your downstream O2 sensors are roughly the same as mine, although mine on Bank 2 seems to be lazy sometimes. I'll keep an eye on it!

As for my data log shot: I am still having troubles using Live Link, it's sometimes showing the graph on the wrong scale, and it looks like it's a flat line. I managed to get some better ones:




On that one you can see that Bank 2 is at ~0V until the WOT (again though, the scale is wrong, it looks like Bank 1 is having a higher Voltage than Bank 2 after the WOT, while in fact it's the opposite, as seen in the current value)
Good point about the EGR, I'll test that one out too!
Cheers

 

[hades_1]

I tested it again and yeah, it looks like my Bank 2 rear o2 sensor is bad, it often goes to ~0 for a few seconds then goes back to normal, so I am guessing it's gone bad and needs replacing. I think a clogged cat would have a more constant reading.

I was testing my EGR as well, but it looks like it's fine going from 130 to 180V:





egr_test_08-06-13b.csv