For those that changed their upstream o2 sensor to increase MPG, did it work?

[TejasRunner01]

I've been looking through a bunch of threads where people were saying that they were getting bad MPG. In many of the threads that I read, people suggested that they replace the upstream oxygen sensor. The problem is we don't know if people ended up doing that and if it worked because they rarely report back.

My question for you who have replaced the upstream o2 sensor as a "maintenance item"; did this actually increase your fuel economy?

Thanks for everyone's reply in advance!

 

[JMat]

Mine actually went down a little...

 

[19963.4lsr5]

It went down for me also. However, engine power increased.


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[TejasRunner01]

It went down for me also. However, engine power increase a little
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Thanks for both of your replies. These are the kinds of experiences that need to be talked about. Keep the comments coming!

 

[gamefreakgc]

Nope. But I fouled mine up pretty good with my tune so it's my own fault. I think I've fouled the one I have right now as well.

However, I am replacing the rear O2 sensor next week when the part comes in. Jury's out on whether it has any affect on fuel trims. Some say yes, some say no and there's data to support both.

 

[LittleCaesar]

Not much of a change. But if you are on the original one, change it with a new one.

 

[4Runner4Leon]

Keeping it unanimous, mine didn't change one bit.

 

[Kanoe]

I'm pretty strict about tracking mileage on mine. I didn't see any change big enough to notice. Was disappointed.

 

[BamaDrewski]

I've been looking through a bunch of threads where people were saying that they were getting bad MPG. In many of the threads that I read, people suggested that they replace the upstream oxygen sensor. The problem is we don't know if people ended up doing that and if it worked because they rarely report back.

My question for you who have replaced the upstream o2 sensor as a "maintenance item"; did this actually increase your fuel economy?

Thanks for everyone's reply in advance!

I have to chime in on this. I have learned (from almost 17 years of experience) when the 02's are crapping out (fore and aft) the engine "feels it". That why I always replace both at the same time. They rarely throw a code.....learned that from experience too....

Bad 02 sensors mimic a bad TPS. You will notice it most trying to go up a steep hill. The engine will be very hesitant. Once they are changed (both) it goes away. Immediately afterwards, you will NOT notice better gas mileage. The ECU has to re-learn the new sensors. If you re-set the ECU by disconnecting the battery when doing this, (swapping them out for new) it has been my experience, you will see an improvement.

I am confident "Little Caeser" will claim it has something to do with my multiple engine oil additives like "LiquiMoly" but it doesn't. 02 sensors are fickle. I keep mine changed out (both) every 2-3 years. That's prolly why I am getting 17-18 in city driving (among other very OCD PM details)

 

[Rallysport]

Tangent, but cleaning my MAF did yield a noticeable improvement in MPGs.

 

[19963.4lsr5]

Just to reiterate that the O2 sensors can go bad and give no trouble codes. I forgot to plug in my front O2 sensor and drove 32 miles to work and got zero trouble codes for it.

Edit: I should clarify. I did get a code for the heater. I didn’t get any codes for the sensor itself.


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[Js'00imited4runner]

Crazy this has been brought up. My CEL light was on when I bought mine (no emissions so no biggie). I've cleaned the MAF sensor probably half a dozen times and disconnected the battery to clear it and it stays off for 3-6 months then shows its ugly head again. Went and got it scanned today and it came up P0136. Before it was P0171. Exhaust needs replaced anyway so I might as well do everything while it's all being replaced. Crossing my fingers that it fixes it once and for all! with 214k its pretty awesome that was the only code that came up! I'm getting about 18mpg average city/highway. So we'll see after its been changed out.

 

[3bears]

no difference for me, was not throwing any codes. Did it as preventative as was replacing the exhaust anyway, and it was 17 years old at the time. Used new Denso

 

[feta]

up

mine went up from 17ish to 19ish, cali spec

 

[SJC4Runner]

It's important to realize that different models in the U.S. use different O2 sensors, so you may see different results due to that. I replaced my California spec O2 sensor and saw about a 1 mpg difference. I went from and average of 15-16 per tank to 16-17.

 

[raKnizek]

Was considering replacing my downstream sensor. Assuming its original at 120k miles and my MPGs have dropped in the last 5k miles or so. Maybe this is not the solution.

I understand why cali specs have different sensors but what is the difference between manual vs. auto, 2wd vs 4wd? Different engine loads mean different expected values?

 

[19963.4lsr5]

Was considering replacing my downstream sensor. Assuming its original at 120k miles and my MPGs have dropped in the last 5k miles or so. Maybe this is not the solution.



I understand why cali specs have different sensors but what is the difference between manual vs. auto, 2wd vs 4wd? Different engine loads mean different expected values?

The powertrain difference it just the cable length because they plug into the transmission wiring harness.


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[raKnizek]

The powertrain difference it just the cable length because they plug into the transmission wiring harness.


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Way less complicated than I was thinking... Thanks!

*Meant to say upstream in my original comment not downstream

 

[gamefreakgc]

So, I've been having some wonky O2 sensor issues and I'm losing MPG's faster than our president is losing approval ratings. Decided to replace the downstream sensor since it's original to the vehicle. Figured it'd help exhaust efficiency but was under the impression it doesn't affect fuel trims at all.

It does!

I have a wideband AEM UEGO gauge hooked up for tuning and at open loop at start up, my engine is always around 12.0 AFR's. Always. I replaced the sensor last night, start it up like normal to go to work and what do you know, it's at 13.5. Anyway, going to write about it a bit more in my build thread.