"Reading" Oxygen Sensors

[UncleRunkle]

OK so I replaced the Pre-Cat O2 sensors on the 01 Caddy DHS tonight and thought I would post a pic of the two sensors from the opposite bank for the boards perusal, the sensor on the right is from the back bank (a real pain BTW) and it seems prety blackened, sooty. What does this mean?

 

[BrianWC]

Looks like the one on the right is running rich. Can the fuel be metered differently for each bank? If not, it could just oil...

 

[soldierman]

If the rear sensor was failing it could have been reporting a lean mix and the computer might have been compensating incorectly. Just a guess though.

 

[UncleRunkle]

Uhh, First off I know my title is jacked up and should read "sensors" not "sansors", oh well, my maximum edit time has gone.

Also, the computer wasn't reporting any codes or anything like that I just wanted to replace them since the car is nearing the 100K mile club. It did have a bit of a surging or "searching" idle during the winter months but it wasn't nearly as bad as idles I've heard on other cars with bad air flow sensors and PCVs.

Also, also, the car does use oil, and .75 quarts of GC every 1500 miles or so.

 

[MiniTransAm]

From my recent experience with 02 Sensors and Cat converters, the rear sensor only reads if the converter is working correctly or not. It does not have an effect on how the engine runs. Only the sensors in front of the cat do that.

 

[tig1]

Originally Posted By: MiniTransAm
From my recent experience with 02 Sensors and Cat converters, the rear sensor only reads if the converter is working correctly or not. It does not have an effect on how the engine runs. Only the sensors in front of the cat do that.




That's correct.

 

[postjeeprcr]

Originally Posted By: MiniTransAm
From my recent experience with 02 Sensors and Cat converters, the rear sensor only reads if the converter is working correctly or not. It does not have an effect on how the engine runs. Only the sensors in front of the cat do that.



From what I read from the first post is the the oxygen sensors both are in front of the cat. It sounds like sensors in the pics are from both sides of the engine. The blacker one being hard to get to because it would be close to the firewall.

 

[UncleRunkle]

Originally Posted By: postjeeprcr
From what I read from the first post is the the oxygen sensors both are in front of the cat. It sounds like sensors in the pics are from both sides of the engine. The blacker one being hard to get to because it would be close to the firewall.


That is 100% correct. These are both the sensors the ECU uses to monitor each bank of the 4.6L Northstar. The Deville DHS only has one main catalytic converter (My jag has one for each bank), and therefore only has one "downstream" O2 sensor.

 

[PandaBear]

Originally Posted By: UncleRunkle
That is 100% correct. These are both the sensors the ECU uses to monitor each bank of the 4.6L Northstar. The Deville DHS only has one main catalytic converter (My jag has one for each bank), and therefore only has one "downstream" O2 sensor.


So one cat for both bank, front sensor to feedback, back to check if the cat work.

From what the OP said it is the rear bank, so does that means it is the O2 for the rear bank? or the O2 behind the CAT?

 

[mechtech2]

The tip is pretty clean.
This slight disparity from side to side may tell us something with new and perfect sensors,but not old ones.

 

[UncleRunkle]

Originally Posted By: PandaBear
Originally Posted By: UncleRunkle
That is 100% correct. These are both the sensors the ECU uses to monitor each bank of the 4.6L Northstar. The Deville DHS only has one main catalytic converter (My jag has one for each bank), and therefore only has one "downstream" O2 sensor.


So one cat for both bank, front sensor to feedback, back to check if the cat work.

From what the OP said it is the rear bank, so does that means it is the O2 for the rear bank? or the O2 behind the CAT?


One cat for both banks, 3 total 02 sensors on the car each bank has it's own pre-cat O2 sensor and one sensor way down the stream to read if the catalyst is working.

these are both the pre-cat 02 sensors, the one on the right is the rear bank of cylinders before the Cat.

 

[UncleRunkle]

Originally Posted By: mechtech2
The tip is pretty clean.
This slight disparity from side to side may tell us something with new and perfect sensors,but not old ones.


Not sure I understand the logic here, if the disparity is there, why can't seomthing be gleaned from it. Regardless of the age of the sensors.

 

[eljefino]

I wouldn't worry, for all we know the front manifold gets better fresh airflow and runs a little cooler or something.

 

[PandaBear]

Is the PCV valve connected to the intake manifold of only 1 bank? If so then there could be a difference in how the exhaust quality looks.

Probably weak ignition on the rear bank or a small amount of burnt oil. You can only tell if you pull the plugs too but not worth the effort.

The one of the left seems to be running hotter due to the whiter color.

 

[hooligan24]

could this be from the rear bank doing all of or the majority of the oil consumption? maybe you should do a compression test and see how they all compare with eachother.

 

[SHOZ]

This O2 was still working properly on my '93 Taurus.

 

[Muffy]

if it runs good, good and fuel, and the light stays off, that means the computer is in happy land and everything is good. the computer is very sharp on detected problems and it will let you know if something is wrong. if it has a intermittent stalling problem then the two crank sensors by the oil filter are bad and would need replacing. they also have to be programmed afterward at the dealer. but just something to keep in the back of your mind. usually that condition happens so fast that the computer can;t catch it and it will just quit but just start right back up.

 

[The Critic]

As a comparison, this is the pre-CAT sensor that I removed from my '96 Saturn SL2 after 115,000 miles. The CEL had been on due to this sensor's failure, which is why I replaced the sensor.

Does anyone know what the white ashy coating means?

I used a Bosch "OE Type" sensor as a replacement. It has been working flawlessly for the last 10,000 miles. OP, what brand/model sensor did you install?

 

[chrome]

Originally Posted By: The Critic
Does anyone know what the white ashy coating means?

I used a Bosch "OE Type" sensor as a replacement. It has been working flawlessly for the last 10,000 miles. OP, what brand/model sensor did you install?


Probably just the various additives in the fuel we get nowadays...

 

[mechtech2]

The O2 sensor[for mixture control, not the second one] is before the cat, and always gets deposits like those .