Downstream Oxygen Sensor SOOTY?
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Downstream Oxygen Sensor SOOTY?
I recently replaced both the downstream O2 Sensors in my 2000 4.2L F150 because I was getting a P0136 (Bank1 Sensor 2) code that I couldn't get rid of by cleaning the connector or fixing wires. 110K miles. Calif truck. No other codes and has always passed smog test easily.
When I pulled the sensors, the DRIVER's side unit was extremely sooty, as compared to the passenger side (bank 1). The code failure was on bank 1.
Is this normal or is there some rich condition on the driver's side bank that I need to check into ?
Originals were Bosch, replaced w/ Motorcraft, if that makes any diff.
One on left is driver's side unit.
Thanks!
When I pulled the sensors, the DRIVER's side unit was extremely sooty, as compared to the passenger side (bank 1). The code failure was on bank 1.
Is this normal or is there some rich condition on the driver's side bank that I need to check into ?
Originals were Bosch, replaced w/ Motorcraft, if that makes any diff.
One on left is driver's side unit.
Thanks!
Lead Driver
Joined: Sep 2006
Posts: 7,907
Likes: 143
Here is an opinion on your situation.
The Ox Sensor location is at the output of the cats for that bank.
Normally the cats run close to 600 degrees temperature.
In a normal engine the exhaust is never that sooty especially at the output end of the cat for that bank.
If the upstream is clean it means the rear heater is not working or the cat efficiency is getting low.
The soot is partially unburned gas or oil that is condensing on a cooler sensor tip. and possibly contaminating the cats as well.
Normally the exhaust does not get through the cats in that state.
Look for the front sensor to be sooty or blacker than the other side as indication the motor has an issue.
If yes look at the plugs on that bank for signs of which cylinder it is.
If no, the cats may be in trouble or the sensor heater is not working.
The rear sensor is only there it monitor the health of the cats.
Good luck.
The Ox Sensor location is at the output of the cats for that bank.
Normally the cats run close to 600 degrees temperature.
In a normal engine the exhaust is never that sooty especially at the output end of the cat for that bank.
If the upstream is clean it means the rear heater is not working or the cat efficiency is getting low.
The soot is partially unburned gas or oil that is condensing on a cooler sensor tip. and possibly contaminating the cats as well.
Normally the exhaust does not get through the cats in that state.
Look for the front sensor to be sooty or blacker than the other side as indication the motor has an issue.
If yes look at the plugs on that bank for signs of which cylinder it is.
If no, the cats may be in trouble or the sensor heater is not working.
The rear sensor is only there it monitor the health of the cats.
Good luck.
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Thanks for the input, Bluegrass. Very helpful... FWIW, I bought the truck new, and since the beginning, the tail pipe has been black sooty, too. Was told it was normal, and since truck ran well, with no codes, I assumed it was true.
But I've never gotten better than 14mpg, city/fwy , 4.2L auto, crewcab, always stock. And I'm easy on the skinny pedal.
I may just take it to the dealer/mechanic to get the injectors cleaned and checked on their super code reader.... Good idea?
But I've never gotten better than 14mpg, city/fwy , 4.2L auto, crewcab, always stock. And I'm easy on the skinny pedal.
I may just take it to the dealer/mechanic to get the injectors cleaned and checked on their super code reader.... Good idea?
Lead Driver
Joined: Sep 2006
Posts: 7,907
Likes: 143
I want to be sure you hear that the sensors should look greyish-white never sooty black in a properly running motor.
To get into why would be practically a book about FI operation.
The short of it is the front sensors hold the fuel very tightly to a ratio of close to 14.6 to 1 for fuel to air ratio.
A closely held parameter like this makes the spark plugs look almost white.
This is why the inexperienced eye cannot tell much about plug heat range in a fuel injected motor because it's normal.
Some old carb boys think the plugs are too hot when they see this but it's normal.
Good luck.
To get into why would be practically a book about FI operation.
The short of it is the front sensors hold the fuel very tightly to a ratio of close to 14.6 to 1 for fuel to air ratio.
A closely held parameter like this makes the spark plugs look almost white.
This is why the inexperienced eye cannot tell much about plug heat range in a fuel injected motor because it's normal.
Some old carb boys think the plugs are too hot when they see this but it's normal.
Good luck.
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GITanker
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