Worth changing O2 Sensor without error code?

[zorobabel]

I changed the upstream O2 sensors this year on both cars, just because they were old. I used the recommended Denso parts for both.

On the the Maxima, monitoring with an OBDLink SX, the LT fuel trims became more lively as rpm and load varied, but stayed the same (+2% for one and +6% for the other) under constant load and rpm.
Mpg was relatively unchanged, if anything I lost 1 mpg - but work on EGR, intake, TB was done at the same time.

On the Corolla, mpg was also unchanged, but I have yet to check the fuel trim post O2 replacement.

I have kept the old O2 sensors...
If I could go back in time, I'd be $150 richer.

 

[dishdude]

NO!

You can make this argument for every part on the car. I wouldn't replace them until they fail.

 

[Wolf359]

Originally Posted By: dishdude
NO!

You can make this argument for every part on the car. I wouldn't replace them until they fail.


The only thing is that if they're cheap enough, they can pay for themselves in improved gas mileage. Say you get an extra 2mpg and you normally get 20mpg and you do 15k a year. At $2.50 a gallon, that extra 2mpg would say you $187. If it were only 1 mpg, that's still over $90. So if the sensors are in the $25-$50 range, it's probably worth doing.

 

[Dumc87]

Originally Posted By: dishdude
NO!

You can make this argument for every part on the car. I wouldn't replace them until they fail.


Define fail?

I've replaced a few with no CEL and saw immediate improvement.

 

[2strokeNorthstar]

See how much they cost. I got a bosch 02 sensor for $14 for my S2000. Made the decision easy. Don't know if it did anything. Only drive the car once a week or less.

 

[ZZman]

So doing some research after posting this it does appear the upstream sensors are the most important for fuel economy and smooth operation. It appears the downstream are really only there to determine if the cat is functioning properly.

I will probably change the upstream ones as both vehicles are near or over 100,000 miles.

 

[LeakySeals]

Originally Posted By: Dumc87
Originally Posted By: dishdude
NO!

You can make this argument for every part on the car. I wouldn't replace them until they fail.


Define fail?

I've replaced a few with no CEL and saw immediate improvement.


I have too. An O2 sensor sits in red hot exhaust gasses for years. And if you have a chronic oil burner the sensor gets covered in carbon. Sensor gets plugged, unable to sense O2. Fuel trim is no longer accurate. Wandering off spec without experiencing a electrical failure CEL.

 

[Malo83]

I have a single o2 sensor on my 83 Silverado 305, change it out every 5 yrs due to slight oil burning, and having to smog test every 2 yrs, staying ahead of the game.

 

[Dumc87]

Originally Posted By: LeakySeals
Originally Posted By: Dumc87
Originally Posted By: dishdude
NO!

You can make this argument for every part on the car. I wouldn't replace them until they fail.


Define fail?

I've replaced a few with no CEL and saw immediate improvement.


I have too. An O2 sensor sits in red hot exhaust gasses for years. And if you have a chronic oil burner the sensor gets covered in carbon. Sensor gets plugged, unable to sense O2. Fuel trim is no longer accurate. Wandering off spec without experiencing a electrical failure CEL.


I've heard the term "getting lazy" when referencing an o2 sensor on its way out. Won't throw a code, but isn't exactly working either.

 

[InvalidUserID]

I've proactively replaced them in my Civic, Camaro and Jeep. Zero noticeable improvement in fuel economy or throttle response. Cleaning the throttle body yielded better SOTP difference.

 

[StevieC]

I replace them when the CEL comes on. If we didn't have smog testing I probably wouldn't at all.