New 02 Sensors = Mileage Increase

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Here is the story.

Over the past year I have been watching the gas mileage on the 96 steadly decline from a consistant 12.5mpg to 11.4 mpg for normal driving. Tank to tank variation is virtually never more than .2 mpg, as the driving that the vehicle gets is very consistant. After poking around a bit, I decided that the most likely culprit was the O2 sensors going slowly south after 147k miles. I gave my CC number to Cdan and a few days later there were two new 02 sensors in my mailbox.


Last weekend I changed out the 02 sensors (with the help of my 2 yo holding the flashlight). Went and filled up the tank at the same station as the last few tanks (mileage for that tank was 11.5) and took the truck home. My wife drove it all week (as she normally does) and I went and filled it up again last night, same station, same pump. Gas mileage is back up to 12.5mpg!!! :D :D :D :D

As a side affect, the truck idles much smoother and runs smoother on the highway.
 
I changed my 1988 62 series with 188k because I was getting a check engine code. Engine idle was dramatically smoother afterwards. I never really checked the gas consumption prior to changing, but I get about 11 city 17 hi-way now.
 
Go Cary!

I'm a firm believer in changing these things out as scheduled maintenance (~100k) whether or not they're throwing codes. I've read up on them some lately, and mostly what I got out of it was that yes, they and their performance slowly and steadily deteriorate. And, unfortunately, their big flaw is that it's apparently very difficult to run an accurate diagnostic on them. (The FSM voltmeter(?) test is supposedly *not* very precise.) Plus they're $pendy.


They're such an essential part of the "closed loop" EFI operation that if they're old and you're having any mileage or smog problems, etc., seems to me you just oughta replace 'em.

Curtis

PS Paragraph 1 info was gleaned mostly from an article in a tech magazine for independent Mercedes Benz mechanics.
 
so, what's cheaper?
new O2s or less mileage?
:)
 
Dare I ask what 2 of these set you back?

I recently realized (despite being under there looking for leaks MULTIPLE times) that the PO eliminated one of the cats so I only have one now:doh: I am now wondering if this has had any effect on the O2 sensors? Possible?
 
The 02 sensors were about $200-250 for both if I remember correctly. CDan can provide the smart shopper price.

According to my calculation, it will take about 12,500 miles to break even for the $250 cost at $3.00 gal if your mileage goes from 12 to 13 mpg. Also, keep in mind that the proper mixture will likely make your cats last longer and save you money over the long haul.
 
I think you would save wear and tear on the engine considering the gas/air ratio would be ideal. Therefore less gas to dilute the oil.
I got my o2 sensors at www.oxygensensors.com for my 3Fe engine for about $70/each. Plugged right in the existing connectors.
 
I changed out one sensor. No change in mileage.
 
Interesting.

I predict a rash of O2 sensor as preventative maintenance threads and mass purchses of new sensors.

I'm pondering it myself.
My mileage has also decreased, but I've got too many other variables (recent mods and wintertime gasoline) involved to jump to conclusions.

Is there a FSM recommended interval for these?

Hayes
 
The difference is between buying an OE with the proper wire harness or a generic with pigtails. I prefer to buy the Factory that I know has the proper plugs that will not get contaminated, rather than screw around with splicing in a universal. Also for the rear sensor, Toyota kindly includes a new plastic mounting tab for the wire so you don't have to worry about breaking the old one.

BTW, Toyota has a nice design for the sensor. It takes 2 13mm (I think it was 13) mm bolts rather than screwing in like a traditional bosch sensor that needs an 02 tool (which I have). Hit the bolts with a little penetrating oil (wurth rost off is what I use) and the things come right out.
 
Hayes said:
.

Is there a FSM recommended interval for these?

Hayes

On a '91, owner's manual and FSM list it as scheduled maintenance every 80k (99% sure on the number; I'll check it tonight). For some reason, a lot of people who change everything else way more often than recommended never get around to the O2 sensors.

Since I'm participating a lot in this thread, I should add a disclaimer: I am NOT claiming changing them will cure whatever ails ya; mostly I'm just trying to point out that they're often overlooked, and that anecdotal evidence seems to indicate replacing tired ones can make a big difference. I'll of course watch along with everyone else as more evidence either pro or con comes in.

Curtis
 
I will be doing my O2 sensors soon as the CEL is on regarding the Sensors and they haven't been changed yet. THe truck has 90K on it.

Are any specific tools required for the job?

Sam
 
cruiserman said:
I changed out one sensor. No change in mileage.

Before I changed both, I changed one only and it made no difference in performance (not good). After changing both sensors, then it really helped.

I don't know if both have to be changed, but it seems like it ( from what I experienced). 88 fj62 w 3fe engine.
 
cary said:
The difference is between buying an OE with the proper wire harness or a generic with pigtails. I prefer to buy the Factory that I know has the proper plugs that will not get contaminated, rather than screw around with splicing in a universal. Also for the rear sensor, Toyota kindly includes a new plastic mounting tab for the wire so you don't have to worry about breaking the old one.

BTW, Toyota has a nice design for the sensor. It takes 2 13mm (I think it was 13) mm bolts rather than screwing in like a traditional bosch sensor that needs an 02 tool (which I have). Hit the bolts with a little penetrating oil (wurth rost off is what I use) and the things come right out.

I agree that having the proper connections is nice, but is it worth $115 vs $65?
https://www.automedicsupply.com/catalog4.php?PHPSESSID=44527876d82041f19329e2056aa0cd30#

Not trying to be critical, but I think four wires could be spliced reasonably well for the difference.
 
PKP80 said:
I will be doing my O2 sensors soon as the CEL is on regarding the Sensors and they haven't been changed yet. THe truck has 90K on it.

Are any specific tools required for the job?

Sam

The CEL light won't come on until long after the sensors are worn out. The general rule is change them at 100k.

See my above post for the tools needed.
 
I bought a pair of NTK sensors for my 91 and it was 79 bucks shipped for the pair. They look like great quality and they come with the factory flange and plug ends. Pretty simple swap. Unplug the old ones and remove them and plug in the new set and install them about a .25 banana job. They are made by NGK who is the leading manufacturer of OEM o2 sensors.
http://www.sparkplugs.com/results_cross.asp?pid=24111&x=24&y=11
Here is a link for them. I believe they also have the sensors for the 1fz.
 

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