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o2 senser question

M

mountainpoo

NAXJA Forum User
Location
HILLSDALE
is there a point in getting a new o2 senser if my check engine light isnt on. i am only getting 10-12 mpg in my 94xj. someone told me not to but i want to do it anyway. also does a throttle body spacer really give you better gas mileage with more horsepower?
 
It's a good start. What size tires, gears, and lift do you have. I'm getting better gas mileage on 33's with 4.56's than I did with stock 3.55's. Once you replace your O2 sensor you could then start replacing other common maintenance items untill your gas mileage goes up. Mine has 215k on it, so when I think a part is ready to be replaced chances are that it should be like in the case of my O2 sensor.

I have a TBS on my 98 F-150. I think it sounds cool, but I don't really know if it helps.
 
How many miles on the existing 02 sensors? Heated oxygen sensors have an "average" lifespan (and that is just ballpark figure mind you) of around 100k. A lot of guys get considerably more than that out of them but over mileage, they do get sluggish and then have a harder time optimizing fuel/air ratio which can affect your gas mileage. Lots of things can affect your gas mileage though.....When was the last time your XJ had a tuneup (plugs,wires,cap,rotor,air filter)?
 
Whoever told you not to change it gave you good advice. If it aint broke, etc, etc... I've found they either work or they don't and the CEL will let you know when they don't. As birch said, look down other avenues...
 
PCM schemes for testing O2 sensors are not bullet proof.
A first indication of a "bad" O2 sensor is an unexplained drop in fuel mileage.
If all other maintenance items are up to date(plugs, filters, plug wires, etc), then I'd summarily change an O2 sensor with more than 80K/miles.
A "lazy" O2 sensor will cause a rich mixture, and will not necessarily set a code.
 
Waterhammer said:
I've found they either work or they don't and the CEL will let you know when they don't.
Click to expand...

Not necessarily true, they can also not work well and not give a CEL. I had one with a screwy heater, it was back feeding and causing stumbling and backfiring, and poor mileage. Never gave me a CEL.

Not saying you have to change yours mountainpoo just pointing out that it could be a cause of the problems, along with many other things. Tune up, fuel filter, etc.
 
Its a 94', I'd replace it anyway. You don't know whne it was last changed. It won't hurt, they are not expensive and its one thing you'll know is good.
TB spacers are a waste of time and money in my book. The money you would spend on on would be better spent on good quality tune up items.
 
Mine is due to be replaced and for $75 it better get me better gas mileage.
 
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