New O2 sensor = better mileage?

[garrett]

Any updates? I usually average around 17 mpg with 265/75/16s... I'm not sure if my o2 sensors have ever been replaced.

[paddlenbike]

Any updates? I usually average around 17 mpg with 265/75/16s... I'm not sure if my o2 sensors have ever been replaced.

It does appear that the mileage has improved. That said, I have only run one tank of fuel through it since the O2 sensor was replaced--it was a ski trip (7,000+ ft of elevation change) along with some city driving. The tripmeter is showing 225 miles with a quarter tank remaining, whereas before the O2 sensor change I was closer to 180 miles by 1/4 tank remaining. Because the bi-product of burnt ethanol coats O2 sensors and makes them lazy, I would suggest spending the $57 if you haven't changed it for a while.

[slomatt]

Option 1: aka "If you are lucky"...

I was prepared for a fight with the O2 sensor tonight. On 5-speed 4Runners, the O2 sensor connector plug is sitting directly on top of the transmission, with no room to reach up, squeeze the plug with one hand while pulling with the other. I read a tip online to remove the O2 sensor from the exhaust and to pass the sensor over the transmission and pull down from the other side, which makes the connector easy to reach. Whomever wrote that tip, thank you, you turned this into a five minute affair.

Option 2: aka "Doh!"

On the first day of O2 replacement you install the rear sensor in 2 minutes, no problem. You then smugly pass the front O2 sensor over the transmission, feeling good that you know the trick to make things easy... and then find out the plug is bolted to the top of the transmission and still unreachable. After 30 minutes of getting grease all over your arm from the front driveshaft and poking around blindly at the connector on top of the transmission you think you've found the release button, but it is buried under 3 other cables and your fingers are numb from trying to press it. You then remove the center console and the shift lever and see if things are more accessible from up top, which of course they aren't. At this point you can somewhat see the connector, but can't reach it. And you can see the bolt that holds the bracket in place, but can't reach it. But, you can see that there is only 1/2" of free wire between the connector and the harness and that explains why you can't get to the release tab from below. Oh, and that cool short throw shifter which raises the shifter pivot point by 2" just makes things worse and harder to access. Defeated you grumble to your wife and have a beer, planning to somehow magically use locking pliers to hold down the tab from the top and then disconnecting the plug from the bottom, yeah, that'll work.

On the second day of O2 sensor replacement you quickly realize that the locking pliers idea is not going to work due to the ginormous short throw shifter housing and the very short leads coming out of the O2 sensor plug. So then you try using other random pliers to hold down the tab but now the tab is just looking a bit beat up. Your initial hope fades. Ok, there's got to be some kind of trick here, what am I missing? I bet I could use a crazy combination of flexible couplers and extensions to get to the bolt that holds the bracket in place, except a: you can't reach it and b: when you finally get a wrench barely on it there is no way you can apply enough torque to remove it, oh and c: you'd never be able to get it back on anyway. Ok, that's it, time to bring out the big guns and drop the cross member so you can lower the transmission and see what the hell is going on up there. Oh, but of course the 4 bolts that hold the cross member in place are on bubba tight and slightly corroded (no other bolts on the truck are of course, just these ones) so after 20 minutes of swearing and intense wrenching they are now loose. The floor jack comes out and you lower the transmission about 2" which is as far as it will go. Shafts of heavenly light shine down and you can now see the f*%#ing connector through the transmission tunnel, but still can't really reach it or the bolt for the bracket. Oh, and both rechargeable LED lights you received for Christmas are now out of batteries and you are starving and really have to take a leak but this is war and there is no time to pause for trivial personal needs. In the dim last gasps of the light you can now see the plastic clip where the plug attaches to the bracket, and after 5 minutes trying to compress it with every pair of pliers you have you finally say screw it and use a combination of a screwdriver and wirecutters to destroy the tab and separate the O2 plug from the bracket, to then realize that the 1/2" leads from the O2 sensor are because some sadistic Japanese Toyota employee (3rd gens are made in Japan) got a little happy with the tape and the wire loom and left no spare wire at all. So, out comes a razor blade and the desperate hope that you don't nick or sever any wires while cutting apart the loom through a 2" hole between the crazy-tall shifter and the sharp steel of the transmission tunnel using the now pretty much not there last volts of the light's battery. Reaching in with your longest needle nose pliers you are able to tear out the last piece of tape, and suddenly the O2 sensor connector (still tightly plugged together) is floating free. Then it's just a simple 5 minute task to pull the connector down from underneath, remove and replace the O2 sensor, run it back over the top, zip tie the connector to the now mangled bracket, and then bolt the O2 sensor in place to the prescribed 14lb/ft (168 in/lb if that is what your torque wrench is happy with like mine is). Victory!! Oh, and then the 15 minutes it takes to raise the transmission back into place, look up the torque settings for the cross member (54 lb/ft) and bolt all that mess back into place. Oh, and then the 15 minutes it takes to put every tool you own back into the toolbox since you had pretty much everything out at some point during this simple task that took ~3 hours over 2 days.


That got a bit long winded, I appologize. The summary is: Pass the sensor over the top of the transmission, if the connector falls down the other side then you are all set. If not, at least now you know the torque settings for the cross member bolts. Oh, and don't install a short throw shifter.

- Matt

[paddlenbike]

I suspect I got off easy. I had work done on my transmission a long time back, and consistent with my theory that "if you want it done right, do it yourself," the mechanic failed to reattach the wiring harness to the clip. Perhaps it was a blessing in disguise. I am sorry for misleading you, perhaps my direction to others would be to cut the clip that retains the harness--it's not like the wiring harness is going anywhere.

[4x4mike]

Yep, Ken got off easy. Matt, my replacement was very close to yours except for the rechargeable lights and lowering the transmission. It did get bad enough that I did consider lowering it. IIRC I didn't have to remove the short shift kit but considered it, even trimming the sheet metal in the tunnel.

My tools of choice were inspection mirrors and seal picks. The SOB bracket is now held in place with a zip tie.

[garrett]

Wow - thanks for sharing mike and matt. I was thinking about doing this soon but I think i will be doing a little investigating underneath before diving in. Would have never guessed it would be this time consuming.

[slomatt]

Wow - thanks for sharing mike and matt. I was thinking about doing this soon but I think i will be doing a little investigating underneath before diving in. Would have never guessed it would be this time consuming.

Garret,

This only applies to 5 speeds, which it looks like is what you have.

There are two relatively easy tests to see how things will go:
1) Unbolt the front O2 sensor, pass it over the top of the transmission and see if the connector comes down on the other side.
2) Remove the shift boot and look through the hole in the transmission tunnel towards the front of the car. See if the grey plug is attached to the bracket or not.

- Matt

[Kryptoroxx]

Matt I experienced the o2 sensor ordeal but it was when I was changing my clutch. I am pretty sure I improved the design when I didn't use that particular area putting it back in.

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