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Discussion Starter #1
first off, here is my predicament...

My check engine light has been on and off for a really long time and finally my gas mileage has droped MASSIVLEY to 10 mpg... then itll sky rocket to around 27 (normal).

I have checked all the normal (fuel filter replaced, gas cap, ect).

would the o2 sensor bring this huge difference? (got it checked at AutoZone)

Which o2 sensor would it be, before the Cat or after and how many wires for the sensor?

I will be having this replaced at a dealership, as you can tell I have little experience, unless someone can help with the directions (have access to the tools, jackstands, all that jazz)
 

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They both should be on the upper surface of the exhaust, basically just under neath the engine. The rear one is next to allways impossible to remove with normal human strength. I think the size of the wrench needed is 7/8th but don't quote me on that.

The tricky part is getting all the clips and stuff undone that hold the wires together all the way to the back of the engine. I would get an o2 sensor specific socket, and a massive cheater bar. I had to use a giant pipe wrench and wedge the exhaust between chunks of cement once to the rear off. If you have a vise taking the downpipe down and letting them soak in penetrating oil for a day is a good idea.
 

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messyroadkil said:
first off, here is my predicament...

My check engine light has been on and off for a really long time and finally my gas mileage has droped MASSIVLEY to 10 mpg... then itll sky rocket to around 27 (normal).

I have checked all the normal (fuel filter replaced, gas cap, ect).

would the o2 sensor bring this huge difference? (got it checked at AutoZone)

Which o2 sensor would it be, before the Cat or after and how many wires for the sensor?

I will be having this replaced at a dealership, as you can tell I have little experience, unless someone can help with the directions (have access to the tools, jackstands, all that jazz)
May want to check your thermostat as well. Has your car been running cooler than normal? If so the thermostat may be stuck open and the car may not be reaching operating temperature. Also check all vaccuum lines and the MAP sensor.
 

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Discussion Starter #5
thanks for all the help guys! just two more things

Which sensor is more likely the culprit and Ive been searching online but do not know the part number, how do I find this out?

*need to order a haynes manual*
 

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Bank1 Sensor1 is usually the problem one on the 4cylinder engines, this is the sensor nearest to the engine, before the CAT. This sensor is used to regulate fuel trim. The other sensor, post CAT is only used to measure CAT efficency, it is not used in fuel metering.
 
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