# which 02 sensor is known to cause bad mpg? how to test?



## se7enty7 (Jun 18, 2002)

seetopic


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## himilefrontier (Jan 21, 2003)

Be more specific.Do you mean which brand or which one on the vehicle?


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## se7enty7 (Jun 18, 2002)

*sorry..*

Which one on the vehicle. I have a98, and I know that there is one on the exhaust manifold, and another near the cat


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## clayk16 (May 3, 2002)

the one in the exhaust manifold


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## BORNGEARHEAD (Apr 30, 2002)

It can be either one. You have to check the code on the ecm and it will tell you which one.


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## se7enty7 (Jun 18, 2002)

its not throwing a code, I'm just getting bad gas milage.


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## himilefrontier (Jan 21, 2003)

The one in the exhaust manifold would be my guess,since the one after it is used to measure Catalytic convertor efficiency. It could be many different thigs though.The only way to know for sure where yor problem lies is to have it put on a scanner.


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## IanH (Feb 11, 2003)

I think the general answer to your question is Yes. 
I had a Subaru Legacy for over 120,000 miles and replaced the O2 sensor, (it only had one,) and the gas milage improved almost back to how it was when new. 
I suspect the O2/fuel ratio control goes off as the sensor gets old.


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## PatScottAKA99XE (Apr 30, 2002)

Its only the front one(mainifold), To test it you need a really good DVOM(multi-meter) or a scan-tool.


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## andre (Apr 30, 2002)

Glad I read this thread....I had just changed my EGR valve, and had the engine light still....I'm getting bad milage, and the guy said it was my O2 sensor (he did a computer analysis), but he never told me if it was the front or rear one. That just answered my question.


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## shmuck90 (Oct 28, 2002)

He told me also that my autosensor is bad, then i said "oh you mean my 02 sensor" and he said yes. So should i replace the front one (which i was going to do)?


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## nitestridar (Jun 29, 2002)

yeah but what is a good replacement brand...

My Nissan dealer want 109-139 for a damn o2 sensor...

but Autozone has some aftermarket one for $80...


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## andre (Apr 30, 2002)

I'm getting Bosch...thats what they got at autozone.


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## shmuck90 (Oct 28, 2002)

the best one is NTK, bosch is alright too.

-Platinum Coated 
-High Purity Sensor Element to Ensure Quick Response to Changes in Air/Fuel Ratio 
-Individually tested
-Easy fitment (oem connector)


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## andre (Apr 30, 2002)

Heck...I paid about $45 for a Bosch sensor today.


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## Ninety-Nine SE-L (May 5, 2002)

where did you get it for $45?


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## nitestridar (Jun 29, 2002)

Andre why didn't you call me I would of went with you....
Noe I have to get bad MPg by myself  j/k

did you get it from autozone?
If so you are gonna have to take aride with me


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## andre (Apr 30, 2002)

Sure Bobby, but when are you going....considering I'll be in school till 7 on Thursday, and I'm off to work as soon as I get home on Friday...Saturday I'll be all over the place...then I got work. Sunday afternoon is cool though. Call me 

The Bosch sensor I got is the OEM spec one, NOT the universal. I made sure to look at the computer screen as the guy did it. I realize that they usually only tell you about the one for about $70, which is the universal one....I just dont see why I should pay more for it. I did get it at autozone by the way.


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## nitestridar (Jun 29, 2002)

I am free Sunday give me a call I you got to take me ...

where did you get it so cheap>


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## sfhellwig (Feb 4, 2003)

*Cleaning the O2 sensor?*

Is it possible to "clean" the O2 sensor? A buddy of mine had a tune-up on his escort and he said the guy cleaned his oxygen sensor. He also had the plugs and wires done but did get way improved mileage. My wife's dad used to clean the plugs in her nova instead of replacing them. Kinda dumb considering the cost but is this a valid approach? Is there anything to clean or do the sensors degrade from the heat? Not to be that damn cheap but I am poor.


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## 97PocketRocket (Jul 31, 2002)

You can probably clean it with some mild engine degreaser or something, if it works and prolongs it even another 6 months then I guess it's worth it, hehe. I clean my plugs about once month using a tootbrush mainly to scrape the carbon off them. It does seem to help keep the idle smooth which is probably more mental than anything but I pull them anyway to keep them from getting locked into the block so the extra 2 min to brush them isn't that big of a deal.


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## Guest (Feb 20, 2003)

Guys, what u mean by a bad gas milage? Is 23 mpg in city mode bad? Could it be better if I replace O2 sensor?


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## andre (Apr 30, 2002)

LOL...in all honesty, 22-23 mpg is all I EVER get....even when the car seems to be in good health. All I get is about 240 miles to the tank with mixed hwy/city (mostly hwy) driving.


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## SilverSentra99 (Oct 23, 2002)

dang man i have a 99 gxe and it has 88k on it and i get better than that, 300-350 miles, on a tank depending on the amount of hondas i get to pick on for the week.
the first quarter i always get 80-109 miles after half im at 189-220 its all down hill after the half and i have my original 02 sensor, and the only mod ive done is k&n Filtercharger. i want better millage though.


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## sfhellwig (Feb 4, 2003)

98' 200sx SE, about 73k, all stock, original plugs and o2 sensors. Haven't logged the mpg lately but 8 months ago when I lived in KC I could pull 400 miles out of every tank without the fuel light coming on. This has probably degraded since I moved to a smaller town and all of my driving is in town. I also don't race or beat on the car in general but do put it through the paces. I intend to do a full tune-up soon and recheck what its getting.


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