Testing Jeep O2, Oxygen sensors

[Royal Nonesuch]

California SMOG update for the metallic Bosch 12009 vs. older ceramic Walker 250-23501.

I drove it for two weeks on the Bosch, watching my renix engine monitor the whole time. It consistently went to closed loop within 20 seconds of engine start (often less), and stayed so the rest of any drive. O2 voltage fluctuated as it should. The LT fuel trim read 120 right before I installed it, and has been between 117 and 120 since. Trips were mostly side streets but included some freeway and one trip hauling a full load of oak firewood. Yesterday I topped off the tank with 9 gallons of fresh fuel, took it for a good fast run on the freeway to get it nice and hot, and went straight to my favorite smog shop feeling confident. There was no one else there so I got right on the dyno.

I passed, but by the skin of my teeth - it wasn't very pretty in the NO category:



The only change I made from 2017 to 2019 was the O2; I purposefully left everything else the same aside from a new cap/rotor/wires. My smog guy remembered how cleanly I had passed two years before and was puzzled as well. He thought it is probably running lean, and suggested possibly the EGR isn't functioning correctly - I will check but I did replace it about four years ago. I brought up the metallic vs. ceramic 02 sensor issue and how I had swapped them - he was interested, and suggested I wait until my next smog in two years and swap back in the ceramic Walker just prior since it functioned so well last time.

Not really sure what to make of this.. happy I passed, but not happy with the results. I wish I could just collect every compatible O2 sensor and get free reign of a CA smog dyno machine for a week to really test it out, but that's not going to happen. It's possible something else is malfunctioning/failing and causing the high NO reading but I'm not sure what that would be - not as knowledgeable as I would like to be on fuel/air chemistry.

Thoughts and prayers are welcome

[randy57]

Originally Posted by Royal Nonesuch

California SMOG update for the metallic Bosch 12009 vs. older ceramic Walker 250-23501.

The walker 250 23501 ceramic o2 is no longer ceramic. Had to send mine back.

[Ecomike]

The Cat converters are two stages, two different Catalytic metals, one the HCs and CO and one for the NOx emissions.

Carbon in the head can raise the NOx, running too hot, and running lean as well as the Cat converter NOx part dying first (and the EGR issue he mentioned) could all be involved. But a lot of folks have a hard time passing CA anyone, especially old rigs...

Thanks for the feed back and all the data!!!

Originally Posted by Royal Nonesuch

California SMOG update for the metallic Bosch 12009 vs. older ceramic Walker 250-23501.

I drove it for two weeks on the Bosch, watching my renix engine monitor the whole time. It consistently went to closed loop within 20 seconds of engine start (often less), and stayed so the rest of any drive. O2 voltage fluctuated as it should. The LT fuel trim read 120 right before I installed it, and has been between 117 and 120 since. Trips were mostly side streets but included some freeway and one trip hauling a full load of oak firewood. Yesterday I topped off the tank with 9 gallons of fresh fuel, took it for a good fast run on the freeway to get it nice and hot, and went straight to my favorite smog shop feeling confident. There was no one else there so I got right on the dyno.

I passed, but by the skin of my teeth - it wasn't very pretty in the NO category:



The only change I made from 2017 to 2019 was the O2; I purposefully left everything else the same aside from a new cap/rotor/wires. My smog guy remembered how cleanly I had passed two years before and was puzzled as well. He thought it is probably running lean, and suggested possibly the EGR isn't functioning correctly - I will check but I did replace it about four years ago. I brought up the metallic vs. ceramic 02 sensor issue and how I had swapped them - he was interested, and suggested I wait until my next smog in two years and swap back in the ceramic Walker just prior since it functioned so well last time.

Not really sure what to make of this.. happy I passed, but not happy with the results. I wish I could just collect every compatible O2 sensor and get free reign of a CA smog dyno machine for a week to really test it out, but that's not going to happen. It's possible something else is malfunctioning/failing and causing the high NO reading but I'm not sure what that would be - not as knowledgeable as I would like to be on fuel/air chemistry.

Thoughts and prayers are welcome

[cruiser54]

Have you ever checked your intake manifold nuts to make sure they're snug?

Common issue and would mimic the symptom of an EGR valve not sealing closed.

[Royal Nonesuch]

Originally Posted by Ecomike

The Cat converters are two stages, two different Catalytic metals, one the HCs and CO and one for the NOx emissions.

Carbon in the head can raise the NOx, running too hot, and running lean as well as the Cat converter NOx part dying first (and the EGR issue he mentioned) could all be involved. But a lot of folks have a hard time passing CA anyone, especially old rigs...

Thanks for the feed back and all the data!!!

Right. I had the head hot-tanked and rebuilt ~5yrs ago and have done a few seafoams since then so it should be pretty clean. The cat is only about 4yrs old, and tempwise she reliably runs about 195-210 degrees according to the REM.

Originally Posted by cruiser54

Have you ever checked your intake manifold nuts to make sure they're snug?

Common issue and would mimic the symptom of an EGR valve not sealing closed.

Good thought - I re-torqued them once a few years ago after I reinstalled the head, but it's seen a heck of a lot of bad Mojave roads since then. Will definitely doublecheck that when I get the time.

Thanks guys!

[randy57]

Originally Posted by Royal Nonesuch

I put in the metallic Bosch 12009 this evening.

Is the newer bosch 12009 still working okay?

[Royal Nonesuch]

Originally Posted by randy57

Is the newer bosch 12009 still working okay?

Yes, it passed smog a few days ago (you can see the stats on that in my post above - it was close) and continues to operate within spec according to the REM. My high NOx content being related to the newer model is still up in the air, but somewhat unlikely in my opinion. If the sensor was incorrect, I don't think the rest of my numbers would have been as good.

I still plan on reinstalling my old ceramic model in two years when I do it again, though

[randy57]

I installed a white porcelain bodied bosch 12009 sensor that replaces factory P/N 4713639. Tested 5 ohms. Had no more than coupe hours idle time due to engine diagnostics testing.

Then the engine began misfiring real bad and wants to die and running vary rich. retested ohms reading on o2 and get no where near 5 ohms.

My diagnostics testing was after fixing a wiring issue that the PO had modified. Basically the o2 heater wire was cut and rewired to the fuel pump relay rendering the o2 heater circuit not working.

Basically because of the PO wire job (don't know why he did what he did), the o2 sensor that was in the engine when I bought it wasn't working at an idle and the engine was ideling rich but had no misfire issues.

It did pass emission with flying colors with the old o2 and heater circuit disabled because the exhaust kept the o2 warm.

Because it was running rich the intake had a lot of residue inside. So am wondering if the contamination in the intake killed the new o2 sensor. But apparently that had no effect on the old o2 sensor.

[randy57]

Originally Posted by Royal Nonesuch

Yes, it passed smog a few days ago (you can see the stats on that in my post above - it was close) and continues to operate within spec according to the REM. My high NOx content being related to the newer model is still up in the air, but somewhat unlikely in my opinion. If the sensor was incorrect, I don't think the rest of my numbers would have been as good.

I still plan on reinstalling my old ceramic model in two years when I do it again, though

Talked to Bosch today and was told that if they changed the white porcelain o2 to a metal body, and if its the correct one (purchased at an approve retailer), there should be a number on the sensor body. 500E263073.

[90xj06]

is the EGR still working? the EGR will lower NOx. check the vacuum lines and wiring and solenoid. a High NOx would be from an EGR not opening.