Is there any truth to that? The theory behind it is when the upstream oxygen sensor gets old, it doesn't switch from lean to rich as fast as it ideally would if it were new. They say fuel mileage goes down with a lazy O2 sensor. My Buick is supposed to get 19/30 but the last year or so it's been getting around 17.5 mpg in town. The oxygen sensors have over a 114,000 on them, so I suppose it's plausible that they're lazy.
Lazy oxygen sensors ?
- Thread starter Merkava_4
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How long are you planning on keeping the vehicle?
Yes. I experienced this on my wifes previous vehicle, an 01 for escape v-6 ,fuel mileage was down never threw and cels. At 130k i replaced the upstream o2 sensor and fuel mileage went back up from 14 mpg in stop and go to around 18. hwy mileage went from 19 to about 23.
Originally Posted By: Donald
How long are you planning on keeping the vehicle?
A very long time. It's been the best car I've ever owned. Very reliable and comfortable to drive.
How long are you planning on keeping the vehicle?
A very long time. It's been the best car I've ever owned. Very reliable and comfortable to drive.
JHZR2
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An O2 sensor is like a solid oxide fuel cell of sorts. The catalyst can sinter, it can be poisoned, soot can coat the surface slowing down the reactions, and the PTFE membrane that protects the oxygen side can get dirty and slow down the transport of oxygen.
I wouldn't characterize it as a fuel cell. It's a solid-state molecular diffusion cell. A fuel cell combines fuel and oxidizer, while this type of sensor generates power from oxygen diffusion alone.
The sensor generates an open-circuit voltage proportional to the difference in oxygen concentration. It generally degrades by a impermeable coating being deposited on the exhaust side of the zirconia sensor. The common coatings are lead (either metallic or an oxide of lead, both from leaded fuel) or silica (ash from silicone rubber). This physically blocks oxygen from part of the surface, resulting in a sensor that has a longer diffusion path and is thus slower to respond to concentration changes.
The sensor generates an open-circuit voltage proportional to the difference in oxygen concentration. It generally degrades by a impermeable coating being deposited on the exhaust side of the zirconia sensor. The common coatings are lead (either metallic or an oxide of lead, both from leaded fuel) or silica (ash from silicone rubber). This physically blocks oxygen from part of the surface, resulting in a sensor that has a longer diffusion path and is thus slower to respond to concentration changes.
Cleaning the O2 sensor is easy. If it isn't totally seized up, and you have some spare time, spray it with electronics cleaner and reinstall.
Don't forget that as it gets colder outside, you'll be running a high-idle for longer periods which uses more gas...so the sensor itself may be fine.
Don't forget that as it gets colder outside, you'll be running a high-idle for longer periods which uses more gas...so the sensor itself may be fine.
The ECM largely has to trust what the upstream sensor says, it really can't tell if it's losing accuracy. Only a complete failure is detectable.
I replaced the O2 sensor on my car and mileage improved by 10%. I was logging my mileage routinely so I was sure of that change. Some people get more dramatic improvement, some don't get any at all.
My car is old though so replacing it was an easy decision. The sensor cost $12 and could be replaced easily, so it's easy to justify. On a newer car it's a tougher decision.
Unless newer sensors work differently, do not use silicone grease on the electrical connector. The sensor actually breathes through that connector as a reference. If you put grease on it, you can mess up it's operation.
I've read many complaints of bad experiences with Bosch O2 sensors, so I'd avoid that brand personally.
I replaced the O2 sensor on my car and mileage improved by 10%. I was logging my mileage routinely so I was sure of that change. Some people get more dramatic improvement, some don't get any at all.
My car is old though so replacing it was an easy decision. The sensor cost $12 and could be replaced easily, so it's easy to justify. On a newer car it's a tougher decision.
Unless newer sensors work differently, do not use silicone grease on the electrical connector. The sensor actually breathes through that connector as a reference. If you put grease on it, you can mess up it's operation.
I've read many complaints of bad experiences with Bosch O2 sensors, so I'd avoid that brand personally.
Replaced the oxygen sensor on a Toyota I used to have and the light throttle ping went away. Never got a cel.
Instead of cleaning & reinstalling, I just replaced it since it had 200k on it.
Was told maybe it was bias on the lean side... I dunno.
Instead of cleaning & reinstalling, I just replaced it since it had 200k on it.
Was told maybe it was bias on the lean side... I dunno.
O2 sensors do get lazy over time, and some OBDII systems detect that... But that usually doesn't work. Instead, it seems they can only detect short circuits, open circuits, and readings that are out of range.
So if the price is low, replacing them does make sense.
Something different happened with my father's Pontiac G6. He had about 100,000 miles on the car and MPG was declining. The O2S had ashes on it, so I got a new one. It made only a tiny change. One month later, there was a MAF error code. I guess when I cleaned it a while ago, it made no difference. The rebuilt MAF I installed cured everything. It suggests to me that a MAF can become inaccurate, but not inaccurate enough to cause an error code.
I have worked with guys who would see the same thing happen occasionally.
So if the price is low, replacing them does make sense.
Something different happened with my father's Pontiac G6. He had about 100,000 miles on the car and MPG was declining. The O2S had ashes on it, so I got a new one. It made only a tiny change. One month later, there was a MAF error code. I guess when I cleaned it a while ago, it made no difference. The rebuilt MAF I installed cured everything. It suggests to me that a MAF can become inaccurate, but not inaccurate enough to cause an error code.
I have worked with guys who would see the same thing happen occasionally.
Originally Posted By: armos
I've read many complaints of bad experiences with Bosch O2 sensors, so I'd avoid that brand personally.
Source?
I've read many complaints of bad experiences with Bosch O2 sensors, so I'd avoid that brand personally.
Source?
Originally Posted By: antiqueshell
Originally Posted By: armos
I've read many complaints of bad experiences with Bosch O2 sensors, so I'd avoid that brand personally.
Source?
Discussion forums revolving around GM cars, mostly OBD-1 era. 60degreev6, fiero.nl, thirdgen.org, jbody.org. I don't have threads bookmarked or anything.
I haven't read much commentary about OBD-2 era, so they may have a different reputation. Among the GM OBD-1 community, Delco and Denso usually get favorable comments and Bosch is more controversial. Some people complain about lack of longevity, some claim their car doesn't run as well with them. Many also report them working fine, but it seems Bosch has a unique level of controversy.
I've never tried a Bosch myself, so if there were a significant price factor involved I might try one anyway. The internet sometimes gets things wrong (popular dogma and echo chamber effect). But the controversy is definitely there.
Originally Posted By: armos
I've read many complaints of bad experiences with Bosch O2 sensors, so I'd avoid that brand personally.
Source?
Discussion forums revolving around GM cars, mostly OBD-1 era. 60degreev6, fiero.nl, thirdgen.org, jbody.org. I don't have threads bookmarked or anything.
I haven't read much commentary about OBD-2 era, so they may have a different reputation. Among the GM OBD-1 community, Delco and Denso usually get favorable comments and Bosch is more controversial. Some people complain about lack of longevity, some claim their car doesn't run as well with them. Many also report them working fine, but it seems Bosch has a unique level of controversy.
I've never tried a Bosch myself, so if there were a significant price factor involved I might try one anyway. The internet sometimes gets things wrong (popular dogma and echo chamber effect). But the controversy is definitely there.
Originally Posted By: armos
Originally Posted By: antiqueshell
Originally Posted By: armos
I've read many complaints of bad experiences with Bosch O2 sensors, so I'd avoid that brand personally.
Source?
Discussion forums revolving around GM cars, mostly OBD-1 era. 60degreev6, fiero.nl, thirdgen.org, jbody.org. I don't have threads bookmarked or anything.
I haven't read much commentary about OBD-2 era, so they may have a different reputation. Among the GM OBD-1 community, Delco and Denso usually get favorable comments and Bosch is more controversial. Some people complain about lack of longevity, some claim their car doesn't run as well with them. Many also report them working fine, but it seems Bosch has a unique level of controversy.
I've never tried a Bosch myself, so if there were a significant price factor involved I might try one anyway. The internet sometimes gets things wrong (popular dogma and echo chamber effect). But the controversy is definitely there.
Add to that my personal, first hand experience.
Denso is a brand that I've never had issues with across multiple application. I'm going to stick with them until I have reason not to.
Originally Posted By: antiqueshell
Originally Posted By: armos
I've read many complaints of bad experiences with Bosch O2 sensors, so I'd avoid that brand personally.
Source?
Discussion forums revolving around GM cars, mostly OBD-1 era. 60degreev6, fiero.nl, thirdgen.org, jbody.org. I don't have threads bookmarked or anything.
I haven't read much commentary about OBD-2 era, so they may have a different reputation. Among the GM OBD-1 community, Delco and Denso usually get favorable comments and Bosch is more controversial. Some people complain about lack of longevity, some claim their car doesn't run as well with them. Many also report them working fine, but it seems Bosch has a unique level of controversy.
I've never tried a Bosch myself, so if there were a significant price factor involved I might try one anyway. The internet sometimes gets things wrong (popular dogma and echo chamber effect). But the controversy is definitely there.
Add to that my personal, first hand experience.
Denso is a brand that I've never had issues with across multiple application. I'm going to stick with them until I have reason not to.
Originally Posted By: antiqueshell
Originally Posted By: armos
I've read many complaints of bad experiences with Bosch O2 sensors, so I'd avoid that brand personally.
Source?
Check out ClubLexus and ToyotaNation. Many, many examples of Bosch O2 and A/F sensors not working. Replaced with Denso and problem solved.
Originally Posted By: armos
I've read many complaints of bad experiences with Bosch O2 sensors, so I'd avoid that brand personally.
Source?
Check out ClubLexus and ToyotaNation. Many, many examples of Bosch O2 and A/F sensors not working. Replaced with Denso and problem solved.
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