If you are getting 17MPG and no CEL, why replace the 02 sensor?

 

From what I've read here, it's the same cost to have the O2 sensor checked vs. replaced. Also, my mechanic said that the 02 sensor gets lazy over time and is recommended to be changed every 3-4 years.

Here's the rationale: The O2 sensor switches very fast between .1 to .9 volts to regulate the fuel. As time goes by, the 02 sensor may still be in this parameter (and won't throw a code) but may not be as efficient as when it was new. Since my truck is a '99 and I will be doing major service, I just figured this would be good bang for my buck. If not, let me know. Thanks.

 

My suggestion would be to drive on a few more tanks with the now corrected MPG and evaluate your results. If you drive pretty easy and stay at a fairly low MPG, then your thinking could be right on. If you do establish a baseline MPG average, say 17.5 for example, then change the sensor, be sure to let us know what you get. If the delta is significant I might consider the change myself (I am at 89K miles).

Keep us posted.

 

Definitely will. I'm at 98K mileage and I drive pretty consistent (I'm on it but never WOT.) I don't keep a log but after each fillup but I always calc what my mpg was from the last fillup, and it's always been around 15 mpg (17 for the odometer correction). There have been a few times that I've been as low as 14+ and as high as 17+ but these have been the exception. Hopefully my mechanic knows what he's talking about...

 

I do the same thing as you do, calculate my MPG. I calculated it before the Air Box mod after I was seeing 17.50 (mostly city) after the airbox mod and before my road trip. After the road trip (also when the CEL came on) I am seeing about 13.09 to 13.90 with one time actually hitting 14.50, but I dont count that one because it was amost all highway that week.

According to URD my new O2 sensor shipped yesterday so I should see it before Friday giving me a chance to install it over the weekend.

I may go for a spin around the whole city and see what kind of MPG I am getting after fixing the O2 sensor.

 

Doublezero, I'm about to go out of the country for a few weeks and I will leave my truck with my mechanic. I asked him about all the service I want done and should I replace the 02 sensor. He said that 3rd gens have four 02 sensors (2 primary, 2 after the cat). Which one are you replacing? He said that although expensive, the age of the car may warrant replacing all. The added benefit would be better mpg. Seems like a pretty expensive venture. Thoughts?

I just read a little more and in seems like we only have 2 O2 sensors and the consensus is only change the front, if required. Please confirm when you get a chance.

 

Thats Odd. I only know of 2 O2 sensors and one MAF sensor. Me personally, I'd replace only the one that needs replacing.

 

Yeah, I have never heard of 4 02 sensors on a 3rd gen. You might want to get the peace pipe from him before you leave...

 

LOL. Thanks. His thought was that V6 OBDII engines have four. I'll ask him to smoke the peace pipe after he's done servicing my truck...

 

One more confirmation for you... We have 2 O2 sensors, and you only want to change the front one.

Have a safe trip!

 

Ditto on that.

He was right on the OBD II wrong on the O2.
The front O2, since it is exposed to pre-cat exhaust, tends to go bad first.

 

Doublezero- let us know if that new sensor helps at all. Still getting the same figures, and im pretty sure my odometer is fine. If so, im going to order a new sensor asap. Thanks

 

I installed the new O2 sensor Friday night and here are my experiences and results:

Installing the front O2 sensor is easier than changing your Oil. I was able to slide under my truck with the following tools and complete the job.

1. - 12mm Craftsman open/box end wrench
2. - Flathead Screwdriver
3. - Light source
4. - New O2 sensor

First step was O2 sensor removal. To remove I was able to loosen the 2 nuts that hold the O2 sensor to the exhaust pipe before the Cat. Once those are loosened you can use your fingers to get them off. Slide the O2 sensor off and be sure to get the gasket that is on there too. From what it looks like there was no type of sealant used and according to the URD instructions I didn't have to use any when I installed. Next you will use the flathead screwdriver to depress the locking clip on the connector to get it off. Shine your light up there so you know which way you will have push to get it off. Its hard to describe this step, you just have to see it.

Now that your old O2 sensor is off take the new gasket that is included with your new O2 sensor and slide it on the bolts. Then slide your new O2 sensor on and put the two nuts on finger tight to hold it in place.

Next take the connector and plug it in. If you bought the URD sensor, then it is a plug-n-play installation. Next tighten the two bolts that hold down the O2 sensor. I went back and forth between the two just to make sure nothing got tweaked...I am that way.

Now that everything is installed double check everything so that you dont have to slide back under your truck again.

Pop the hood then go to the fuse box that sits directly behind the battery while standing in front of your truck. Remove the cover and look for the 20A fuse for the ECU. Its location is in the lower quadrent 2nd from the top. To remove the fuse Toyota has included the tool you will need to remove it. It is located on the inside of the cover you just removed. After you remove the fuse, replace the fuse. This will reset your ECU. Replace the cover, close your hood and go wash your hands.

Now take the truck for a drive and enjoy - you are done. My installation took more time to get my tools, put them away, wash my hands and tell my wife about how easy it was than the actual installation. She was actually coming out to the garage to ask me if I was going to install it and I was tightening everything up and told her it was done.

Aside from replacing a fuse, this was the simplist install that I had ever done. I wish I had done it two months ago when the problem started. Could have saved some money at the pump.

Now for the numbers:

Before installation my last MPG was 14.87 this is a combo of City and Highway. This morning after driving 98.7 miles I re-filled for the week and was seeing 18.69 MPG with a combo of City and Highway (note: there was a bit more highway driving over the weekend but still a decent mix of the two.) My research was right about the ECU jamming in more fuel than necessary and causing my crappy mileage. (happy dance here)

Special Note: Before i replaced the O2 sensor I would notice an above normal exhaust smell when backing into the garage. I would also get this smell when driving with the rear window down. Now I do not get this and tried both highway speeds and city/ stop and go driving.

 

Doublezero, please post some more mpg number in the next few weeks. I'd be very interested in seeing how much improvement you got by doing this. Also, do you know if there is a recommended interval of replacing the 02 sensor? I haven't seen anything as far as Toyota is concerned.

 

I wouldn't know anything about a reccomended interval, what I do know is that I have owned 3 Camry's and 2 4Runners and I have replaced my O2 sensor on my 96 Camry at 80K and 170K. My 2000 4Runner - it went at about 92K. I would be happy to post more MPG numbers as I get them in; I usually re-fuel once a week.

 

Did you replace because of a CEL or b/c of the gas mileage issue? My truck is at 98k so I may be needing one but no code as of yet.

 

Yes, I had a CEL.

P0130
P0133
P0171

Those were the codes it was throwing and they would come back after a reset anywhere between 50 - 100 miles. Its now been 130 miles and no more CEL.

 

Yeah im gettin the numbers for mpg double zero got, yet i havent had a code thrown since the po171 2 months after the k@n....took it to the dealer, and they either cleaned/repleaced the MAF. ....I have heard about cleaning the o2 sensor...what do you guys think about that???? is that possible with a acetyline torch and wire brush????? thanks

 

I don't suggest ever trying to clean an O2 sensor......remember the part that needs cleaning is under the metal tip not the tip itself. Top end cleaner would work the best if you are going to try it then rinse with electrical cleaner. If it were my truck I wouldn't waste the time and just install a new part.

 

Replace your O2 sensor. Don't try to clean it. The O2 sensor was $94 an some change shipped and was installed in no time. Mind you I live in Phoenix so we dont have road salt issues.