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which o2 sensor

lsneo

CEG'er
Joined
Sep 16, 2002
Messages
53
Location
Houston Texas
ive been getting terrible mpg and im thinking it might be the o2 sensors. No cel, i need to know which one to change for better gas mileage or should i just change both.
 
I'd clean your MAF and IAT first along with replacing the airfilter if you haven't already. How many miles are on your car? Maybe replace your spark plugs and ignition wires if you think it needs it. Also run an additive in your next fill up to clean the injectors.

That's all I can think of off the top of my head.
 
What is your average MPG? What was it before?



If you dont have a CEL on for the O2 sensor it is probably just fine. if you still want to replace it it would be the upper one before the Cat
 
You didn't metion what you done before so I just gave you tips that could be a culprit to your bad gas mileage. The O2 sensor is very sensitive to change so if there is no signal/CEL then it should be fine. Have you checked your fuel filter?
 
yea ive checked every filter, changed/cleaned all the usual stuff. The car doesnt have a hard time starting.
 
what year and tranny is it?

there was something wrong before cause even in the city you should get much closer to 300 miles per tank
 
Zetec with auto tranny, I was ok with 200 since I do have a heavy foot. The car is a 2000 with no mods other than exhaust.
 
i have a heavy foot too and i get over 300 mostly city with some highway.

see if you can have the car checked for any pending codes.
 
Are you filling up at the same gas station all the time? Are you comparing to prior to ethanol becoming "mandatory". Maybe it is due to the ethanol content. Remove all unnecessary "junk" from the car. In addition, check your tire pressures. Have you been using the DEF or FLR/DEF a lot lately? This turns on the A/C and that thats a lot of energy from the car. Is your rear parking brakes locking up in the morning?
 
The guy is right. Oxygen sensors become less responsive with age. And considering the price of gas, you might as well throw a new one on there if your car is getting up there in miles (Id say 90k would be a good time to replace). What a new sensor costs could save you lots more in gas over several months.

Try oxygensensors.com, and its the upstream one (in the exhaust manifold).
 
it will run you about $70. i just replaced mine this past weekend.

keep in mind thats from autozone and im sure you can find one cheaper.
 
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