O2 sensor a maintenance item?

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Donald

Donald

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Does anyone replace the O2 sensors at a given mileage? Say 100K? Upstream or downstream or both?

Without any codes.

Does this increase mileage? Anything else noticeable except less $$ in wallet?
 
They do wear out and cause mileage to decrease.

Is this for your Grand Cherokee? I would replace the O2 sensors along with using better injectors. You'd see a 10-15% increase in fuel economy!
 
BMW specifies a 120k replacement interval, FWIW. I've seen them go much longer, and seen them fail before that. Best thing you can do (other than replacing them) is to spray the sensor with some electronics cleaner.
 
Originally Posted By: Miller88
They do wear out and cause mileage to decrease.

Is this for your Grand Cherokee? I would replace the O2 sensors along with using better injectors. You'd see a 10-15% increase in fuel economy!


Better injector as in what way? A better brand than OEM?

Yes, for Jeep.
 
Last edited:
At 60K my 2003 Dakota 3.9 was cold starting rough with wandering fast idle and had lost 1+ MPG. I changed out upstream O2 sensor with a new Echlin one. All problems fixed, didn't even unhook battery to clear memory.
 
If your tailpipe is black and you are experiencing sub-optimal F.E. and have a non turbo, you may be running off stoich and may be in need of a new Lambda thimble - Al long as the front end ( metered inlet) airstream is all tidy.
 
My mom's 1981 dodge omni miser did not have a check engine light.

However, it had an "o2 sensor" light that lit at, IIRC, 60k to remind the driver it was time for its regular service.
 
Originally Posted By: dparm
BMW specifies a 120k replacement interval, FWIW. I've seen them go much longer, and seen them fail before that. Best thing you can do (other than replacing them) is to spray the sensor with some electronics cleaner.


??? These things are like a solid oxide fuel cell with a PTFE membrane. What would you spray with cleaner?
 
Originally Posted By: Donald
Does anyone replace the O2 sensors at a given mileage? Say 100K? Upstream or downstream or both?



I dont think Id ever replace downstream until I saw a CEL.

Ive heard that upstream sensors get "lazy", and either take longer to warm up and/or dont switch fast enough and throw the controls approach off...
 
I finally replaced the factory original o2 sensor on my 92 Accord last month because I was replacing that section of pipe. I haven't noticed any increase in gas mileage or performance. I will not replace them unless they're causing problems now.
 
Just replaced the original sensor in my 94 accord @246k. Finally threw a code for the ox sensor heater circut. The sensor still worked fine, but the electric heater that helps it warm up faster must have grounded out. Seperate code from the sensor.
It does run very well now but i did not get a wild increase in milage, just back to normal as it did drop a couple mpg when the heater went out.
 
Originally Posted By: Donald
Originally Posted By: Miller88
They do wear out and cause mileage to decrease.

Is this for your Grand Cherokee? I would replace the O2 sensors along with using better injectors. You'd see a 10-15% increase in fuel economy!


Better injector as in what way? A better brand than OEM?

Yes, for Jeep.


The ones in our 4.0s are single stream injectors. There are 4 port injectors that came in Neons and some Fords that are a direct swap.
 
I replaced my upstream O2's at about 80,000 miles because I had read they do get slow and lazy with age. I replaced my MAP sensor at the same time and I did notice MPG went up a little. The more noticeable improvement was my truck's power and general get up and go got a little better. I don't know if the MAP helped or O2 helped or they both worked together. I am looking at possibly replacing one upstream O2 again now that I have a catalytic convertor problem with my truck. NTK is the MOPAR OEM supplier. Rock Auto had the best price I could find on NTK's.
 
For Jeeps, they say to replace the O2 sensors at around 150k miles for best results. Use only NTK sensors since they are what came from the factory. Some have used Bosch and got worse mpg. Not saying everyone who used them experienced that, but why chance it? I installed NTK sensors in mine which has the 4 sensors around the mini-cats like yours should have, and noticed a 1 mpg gain.

Unless you suspect a problem with your injectors I would leave them alone. There are many threads about upgraded injectors on the jeep forums and they don't seem to do anything unless your old injectors were clogged up. I tried the 4 hole injectors from precision injectors. They ended up leaking down after sitting over night and causing hard starts. The customer service was good, but after two sets that did the same thing, I just put the old injectors back in and asked for a refund. Getting your old injectors cleaned and rebuilt would probably be the best option, but then again I wouldn't mess with them if they work fine.
 
The idea that it is necessary to replace O2 sensors as a regular maintenance item was/is perpetuated by those that manufacture and/or market O2 sensors. The odds of purchasing an aftermarket O2 sensor that will have the longevity of the factory O2 sensor, or is "better" in some way, are slim and none, regardless of the brand name on the outside of the box.

Keep in mind that a failing O2 sensor does not cause an immediate catastrophic failure. Vehicles are required to have systems in place that alert you if there is an emissions related problem, so there is no need to replace a good sensor with one that is the same or worse.
 
Yes i let them go to about 100-125K then swap the upstream out. The older the downstream is and still functioning the better it is at keeping pesky P420/P430 away.

The injectors in those engines were reliable enough they just didn't atomize very well.
The single stream in a 2V head is fine, they can however cause cylinder wall wash down when one goes a little lean (dirty) and the PCM fattens the rest up attempting to maintain stoichiometric.

As someone posted there are better more modern alternatives as far as injectors go, they are not very expensive.
 
Originally Posted By: KB2008X
The odds of purchasing an aftermarket O2 sensor that will have the longevity of the factory O2 sensor, or is "better" in some way, are slim and none, regardless of the brand name on the outside of the box.


Based upon what?
 
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