Oxygen Sensor
 

my check engine light keeps coming on in my explorer...had the code read and it is a bad oxygen sensor. Will this affect my fuel mileage?

It can cause several things to go nuts, besides bad mileage. The Ford wiring system seems to be a little less sensitive than most, been running around for 2 years with a bad one on a F150 V6 I drive.
Had a Chrysler minivan, the dealer convinced me it was a bad transmission, 2 weeks later did the same thing, ended up being one of the sensors.
The Jeep Cherokee suddenly ran like crap, wouldn't idle or accelerate, smutted all the plugs, had to change 2 sensors to fix the problem.
Try to remember what the code number was or the defining sensor, you should have 4 on that thing, some are a booger to get to and some are in the open easily accessed.

If it is the sensor, then search on google for cleaning the sensor.

Family Handyman or Mechanics Illustrated did a story on how to clean the sensor,
because some unscrupulous mechanix where charge for a new one with installation,
when in fact it just needed a good cleaning.
It is a piece of wire tha gets a shelac coating on it and when the coating gets too think,
the electronics think it to be bad.
It will affect your milage, if I recall from the article.

If you can get to the end of the sensor, spray it good w/some contact cleaner...that'd be my first try at it...

Okay guys, now you are poking around in my area of knowledge.

An Oxygen sensor is mounted in the exhaust system, some vehicle have multiple 02 sensor. Tey measure the amount of oxygen in the exhaust gas and it generates a voltage signal that the engine controller uses as a signal to alter the pulse width on the injectors to control the air/fuel ratio.

They are screwed into a boss in the exhause pipe and can be a pain to get out, they usually require a special 6 point socket to remove. As far as cleaning one, that might be a bit difficult as they run at such high heat that anything that would end up on the business end of the sensor will turn to carbon, and carbon is very hard at best to remove.

IMHO, If I went thru all the trouble of determining that the 02 sensor is bad, and took it out, I'd likely spring for a new one.

Just sayin..........

I'm agreeing with Franco about replacing it but then I'm just lazy.
If I have to remove spark plugs, they get replaced. If I have to check the air filter, it gets replaced. If I have to take a taillight lens off, the bulb gets replaced.

What year exploder? What engine? How many miles? Yes they can just fail, most times a cleaning does nothing for them long term. And remember that a code is just a diagnostic tool, not a definitive answer. Many other things can throw an O2 sensor code as well. If the O2 did in fact fail and go to an open circuit, then the PCM will not have any data to adjust the fuel mixture for changes and can seriously affect your milage. Like Franco said, it is basically a fine piece of wire that reacts to temperature and changes the voltage that it can conduct and relays the voltage change to the PCM to tell it what the fuel mixture is. Also most O2 sensors since the late 80's are now heated so they can give better readings at low engine output levels. If the heating element burns out this can also throw an O2 sensor code, but will not affect your cruising milage that much going down the road.

This is why most shops hate AUTOZONE who tells people they have an O2 code and say a new one will fix it. Something like a blown exhaust gasket, plugged cat converter, weak plygs, plugged fuel injectors, blown intake gaskets, or even a blown head gasket could show up as an O2 code. I even had one truck one time that had a bad coolant temp sensor and a stuck open thermostat pop an O2 sensor code, yet the O2 sensor was fine. The engine was running too cold and couldn't burn the fuel which in turn popped an O2 code.

Well then...let's sh!t-can the thing about sprayin contact cleaner on the tip...the Pubah has SPOKEN!!...LOL!!...

Ferm...98 explorer, 5.0 litre V8, 158,000 miles.

oh and the darn ABS light wont go off either???

thanks for the input fellas

What is the code? Most O2 sensors also have a heater inside them, so that it takes less time to go into closed loop operation(ECM/PCM controls injector pulsewidth to reach proper air/fuel mix, instead of running on a preprogrammed parameter.) If you haven't noticed a drastic change in fuel economy, than I prob wouldn't replace it yet. Just becasue the heater dosen't work, dosen't mean the O2 side isn't functioning.