replacing 02 sensors

[Timothymoore1979]

I have a 2004 xlt explorer 4.6 2wd. Im desperate to help the gas mileage, im getting around 10 mpg city. I read around and think its best that i replace the 02 sensors as it has 170000 on it. I called autozone to get sensors and they dont have a clue as to how many i need...i know...so i called ford parts and they started talking upstream, downstream, bank 1, bank 2. Im not a mechanic but i know where they are just dont know about the upstream and bank thing. please help.. if i knew whick sensor was which then i think i could do it myself. I have 2 before the cc and 2 after ..
.. thanks to anyone who is willing to help

 

[BIGTREAD]

Do you have any evidence that it is the O2's? They're not that cheap, and there are lots of things that could contribute to poor mileage. Any codes?

 

[ExPlOrErImPoRtS]

They are easy get nice blanket to lay on . the ones upstream is closer to engine they are a little harder more vertical part of the exhaust . helps to get front wheels on ramps at least. I replaced all 4 at 110k


make sure get oem style connecter. would suck if you have to splice into all the wires plug in play is better.

 

[Timothymoore1979]

no codes just thought changing all of them might give me a little hope on mpg...I cant take it. She doesn't have a leak or at least i dont smell gas at all. seems like if i move her across the yard to mulch leaves she loses a quarter tank. maybe not quite that bad but it sure feels like it...put it this way. i filled her up and she has 154 miles on her and a little less than half a tank on a 22.5 gallon tank. we have not used a/c at all

 

[LONO100]

before you change the O2 sensors, make sure you have loked into all of these other things that could be the culprit. some of them seem pretty obvious and you may have already looked into it, but just listing all of the things i would look into before touching the O2 sensors.

-air filter
-motor oil
-fuel filter
-spark plugs and wires
-tps
-egr
-pcv
-MAF
-throttle body
-checking all hoses, elbows for cracks
-vacum leaks, vacum leaks, vacum leaks! check, and then check again, and then check again
-upper/lower intake manifold gaskets

if it were your sensors malfunctioning, you would get some sort of codes, so usually its not the sensors. im sure you have looked into most of these already, just thought id make a list in case you may have missed something obvious.
good luck!

 

[Timothymoore1979]

I now have a P0401 code...EGR insufficient flow...could this be my culprit??? on mine the dpfe sensor is mounted with the egr valve (i think). i check all the hoses the look good. replace the egr valve???

 

[LONO100]

i would def look into changing the egr valve before messy with the O2 sensors. there is even a thread on this forum that shows you how to clean it. you might even want to try that route before buying a new egr because they can run a few bucks, but i suspect you will end up having to change it out. try cleaning it first, then see what happens. and check all your vacum lines again just for good measure, im telling you, its real easy to think you didnt find any cracks but they always show up upon second inspection!

 

[Timothymoore1979]

thanks alot... im off tomorrow and gonna change plugs oil and filter.they had a special on Pennzoil...so i got the 5w20 synthetic with kn filter and motor craft plugs with engine with 150000. does all sound good??? oh and clean egr valve and replace fuel filter

 

[LONO100]

sounds like a good place to start before fiddling with the O2 sensors. when you buy the fuel filter, get the little line disconnect tool. i havent done mine yet, but ive heard that the fuel filters on these trucks are a nightmare to pull off. while you are there, get the MAF cleaning spray and get your MAF cleaned too, it helps a ton in terms of getting your MPG down, and getting a smoother idle. make sure to treat that thing as careful as possible because it costs a grip if you mess it up! good luck and let us know if you get your problem fixed.

 

[BWheetley]

no codes just thought changing all of them might give me a little hope on mpg...I cant take it. She doesn't have a leak or at least i dont smell gas at all. seems like if i move her across the yard to mulch leaves she loses a quarter tank. maybe not quite that bad but it sure feels like it...put it this way. i filled her up and she has 154 miles on her and a little less than half a tank on a 22.5 gallon tank. we have not used a/c at all

I usually only get about 300 miles on a full tank in my 02 Sport Trac. I figured thats about normal. My GPS tells me I'm getting about 18 MPG on highway and 15 in city.

 

[RickM]

If replacing the O2 Sensors then consider using Bosch Universal sensors. Many parts stores carry them and they're much less expensive. With "Universal" units you clip the connector off your old sensors and use the included (waterproof) splice to attach to the new sensor.

I replaced 4 sensors on a 993 twin turbo and they worked like a charm.

Below are the Bosch part numbers for both OE (with connectors) and Universal (w/o connectors).