Well - for those with mpg woes...I replaced my front 02 sensor a while back and my mileage has gone way up

I was getting 250/tank - that has now moved up to around 300

 

and here is what the old one looked like after 65k!

 

maybe i should do that.....i only get around 200 per tank

 

Wow, that's great. What type of MPG were you getting before the change? I am at 17.2 or so, and I feel it should be better. I am wondering if that sensor has anything to do with it. 86K miles here.

 

yeah - matt, honestly didnt expect such a big increase...I know some people replace theirs w/o effect.

But I would say it is worth a shot.

I am an idiot so it took me a long time to install it; but it should really only take 1/2hour or so.

 

Christian

I was getting about 16 mpg - it is now around 19-21mpg!

 

jon---is there any specific type of o2 sensor i should get?

 

Matt,
Get Denso OEM -
aftermarket o2s supposedly can be a problem.

This was discussed earlier - but Gadget has fantastic prices on OEM o2 sensors:
http://www.urdusa.com/Merchant2/merc...tegory_Code=O2

otherwise expect to pay between 115-140 at a dealer

 

Anyone ever had their O2 sensor pop right off?
Mine did, about two weeks ago. I had heard that removing this was a PITA. Imagine my surprise when I saw mine hanging under the cat, no nuts on either stud. I can't swear that it was actually bolted down, as I never had cause to look at it. But I was driving home one day and thought the truck next to me was kinda loud. Then he passed me and the noise was still there. Sure enough, it was ME!
Can anyone tell me the correct size/pitch for these nuts...I need two new ones.

 

My 1995 SR5 12mm O2 sensor braket nuts...

I took my front 02 sensor off a few days ago without anything but alittle leverage as they weren't rusted up too bad.

After removing from the exhaust I cleaned it out with some solvents with quite a bit of junk come out of it..... I just filled up with gas today and will report back if I see an obvious increase in MPG.

I dind't feel like buying a new one since they're fairly pricey so I thought why not experiment with cleaning it first to see if that does anything...

Tom

 

Midi-

Thanks! I would really like to also replace 02 sensor, in fact I have tried. I spent an hour and a half trying to pry it loose, but the bolts are incredibly rusted and corroded. I have been advised to use a torch...can I get one of those from an auto store? Even if I did get one I am not sure I would know exactly what to do with it...so I guess I am erring on the side of spending twice as much and taking to my mech.

If there is a way for me to use a torch myself and I can pry it all loose without damaging anything I have heard from the dealer that for my year (1999 sr5 4runner, v6) there are actually 3 DIFFERENT manufacturers for the front 02 sensor...is this true? He said you have to match up a number on the sensor...which I also cannot find because of all the rust...yikes.

If anyone thinks they can help me do this right on my own that would be awesome!

thanks....

 

Wow thats quite an increase you got there. I want to replace mine too but I dont know if it would do any good. My mpg problems are all city driving. Even with tons of hills and stop and go traffic, should I be getting a huge difference between city and highway mileage? I avg about 12 mpg city and about 19+ highway. There shouldnt be any difference between the o2 readings when you're going a constant speed and when you're stopping and going right? A new o2 sensor is about the only maintenance thing I have left to do in the usual mileage increasing suggestions (change filter, oils, plugs etc) but dont know if it would do any good.

 

hmm, only things i can think of would be... that you might just be a lil heavy on the pedal accelerating for that much of a gap in mileage. do you have an auto or standard? if its a stick, a reason for the mileage could also be your waiting too long to shift? (4500+ rpm range)

 

Nope, driving at less than WOT (Wide Open Throttle) is _ALL_ about the front O2 sensor. This is how it works...

When you're generally cruising around town, the ECU (computer) is in "Closed Loop" mode. This means that the ECU is using the front O2 sensor to make a lot of it's decisions on how much fuel to dump into the engine. In Closed Loop, the ECU will do what it can to get the engine to run at a air-to-fuel ratio ("A/FR") of 14.7:1. This is called Stoichiometric Conditions, and is the optimum ration of air/fuel for complete combustion (but fwiw, not optimum power).

When you slam the pedal to the floor, the ECU kicks into "Open Loop" mode and basically ignores the front O2 sensor in terms of worrying about fuel delivery.

Okay, back to closed loop...

The O2 sensor will read each "puff" of exhaust as it comes by, and it reacts pretty quickly. By the normal nature of these engines, the cylinders really don't run the same fuel mixture, and as such, the O2 sensor will read a different A/FR for each exhaust cycle. That causes the ECU to see a varying number, and as a result, it will react constantly and adjust the amount of fuel based on the last O2 reading. If you were to watch this with a A/FR meter, you'd see it swing pretty widely.. mine runs from about 11:1 (lean) - 16:1 (rich). The best that the ECU can do is to react along with the O2 sensor and try to hit a value that will place the engine at 14.7:1 on average.

Now... if the front O2 sensor is clogged, "tired", old, etc. then it will be slow in reacting to the changing A/FR, or not react with it's full swing of voltages. If that happens, then the ECU will tend to push the engine to run rich, and over the course of a tank, that causes pretty poor gas mileage.


In short... The O2 sensor is often skipped over when trying to fix poor gas mileage.

 

You can use the torch to heat the area around the bolts, hopefully causing it to expand and loosen the bolt up a little. WD-40 or some other kind of penetrant can be helpful here too. It usually just takes patience and elbow grease.

I don't really know about the 3 manufacturers...guess you'd have to take it out and bring it to the dealer to match it if that were the case. Hope you have an alternate vehicle!

 

i feel enlightened.

sorry to jack the thread but... does anyone know a good place to get oem sensors for a 2nd at a great price?

 

yea I was planning on doing it last night, but due to it taking longer than expected to cut, weld, and grind my a-arms, I didn't have any time. Plus I haven't ordered it yet haha.


Christian, you're beating me in miles now! I'm at 90k

 

I'm with green91runner. Does anyone know where to get 2 gen OEM O2 sensors at a good price?

 

Thanks Mark! I was only hoping to get a yes or no answer with maybe a short explanation but this is great. I also feel enlightened. Looks like I'm gonna get me a new sensor.

 

"Beating" you as in I have less, right? It just sounds funny the way you worded that. I am beginning to worry about your addition and subtraction skills. I thought you were an aspiring engineer dude, c'mon!