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Discussion Starter #1 (Edited)
I just swapped out the two O2 / 02 sensors and figured I take some pics and post.

I had taken off the intercooler (easy) to change out the plugs with OEM plugs at 72k miles. At that point you have more space to get a ratchet onto the upstream sensor.

YOU WILL NEED TO PUT THE CAR ON RAMPS or jackstands.

Here is a picture of the upstream sensor near the firewall from the the passenger side.



Having the intercooler off allows a straight shot to the sensor with a 1/2 inch driver, 5-6 inch extension and a 7/8ths inch oxygen sensor socket.

Like dis:




Make sure you get under the car and unclip the TWO yes 2 connectors coming off of the upstream sensor. They are not easy to unclip. The trick is to push down on the release tab as hard as possible and then pull them out. You will only have room for one hand at a time so prepare to get slightly annoyed. Eventually you will get it off. Just dont tug on the harness.

Here is a picture of the two connectors (grey and black, bottom of photo) from under the car....and yes that is my greasy ass turbo dripping down onto that pipe...wish I had noticed that before the damn warranty expired!



After you unplug both connectors, you have also unclip the white plastic clip that holds the harness to the metal bracket which supports the 2 connectors. You can just pull on it till it breaks free or use needle nose pliers.

Then you have to unwrap the wire from two of these metal curly things which keep the wire away from hot exhaust parts.



One of them you can see from over the engine bay, the other one you will feel with your fingers but not actually see while you are under the car.

You must disconnect and pull that wire up to the engine bay before you put the 7/8ths o2 sensor socket on the sensor to loosen it. Like this:



Both my sensors came off no problem. I did not need to apply any PB Blaster or any such thing. Engine was slightly warm at the time. You can get to the upstream sensor without taking the intercooler off, but you will need to use a universal joint and that is always most annoying.

I think the torque specs is like 25-33 foot pounds for the replacement sensor. You just have to crush the metal washer...don't overdo it. You don't wanna crack the damn downpipe.

As for the DOWNSTREAM SENSOR, once you have the car on ramps, you can get to it as well. You will need to unplug the harness, which is just to the left (from under the car) of the two connectors for the upstream sensor. Unclip it (good luck) and then bring the wire down so it can rotate with the 7/8ths or sensor socket.

Sorry I don't have any pics.

Unlike the UPSTREAM, this second sensor is harder to get to with a ratchet. Because my Craftsman 7/8th o2 sensor socket is so tall/long, I couldn't fit the ratchet into place and have any space to turn on it, so I used a 25mm open ended wrench on the top of the 7/8th inch socket. In this way I had enough space to turn on the 7/8ths socket.

BTW, when youre taking off the intercooler, be careful not to drop any of the washers into the engine bay. Sometimes they stay on the engine, sometimes they stay on the intercooler...just make sure you keep track of them.

They look like this:







Here is the new and old upstream o2 sensor side by side.



It annoying to do on your back but you can do this job and save a crap load of cash. I made the mistake of buying the upstream from Montgomery Mazda online. You can get the OEM parts from ROCKAUTO (made by NTK) for much much cheaper.
 

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Great post. Should be a sticky. I'm always afraid those sensors will seize in place depending on mileage. Thanks. Any improvement in performance/mileage?
 

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Good write up man.

You just reminded me of the pain...lol

Those 2 connectors suck.

Especially when the car is hot. Got a couple burns messing with them.

Acutally pulled the battery to get loose the grey one I think.

Second round got from underneath though.

Used a breaker bar with socket on downstream. Yup tight spot for ratchet to fit.

Downstream not bad except for space.

Uptstream connectors suck. Cable route is a pain. Once you get unwrapping from the coil not bad. Connectors suck...again.

I went with denso from rockauto. Wil be interesting to see how they hold up since previous were NTK.
 

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Discussion Starter #4 (Edited)
Great post. Should be a sticky. I'm always afraid those sensors will seize in place depending on mileage. Thanks. Any improvement in performance/mileage?
I hope the pictures help the next shadetree mechanic.

As for any improvement? Well....this was a 2 stage job. First day I did the plugs and upstream O2 sensor. I bought those parts from Montgomery Mazda online. Car ran great. Felt super responsive.

Second stage was the serpentine belt (OEM) and downstream O2 sensor (NTK from RockAuto) which I installed the following weekend. Ever since then the car has been running real poorly. MPGs are down a few points as well. Im halfway through a second tank of gas since the NTK O2 sensor was installed and car is still running like doodoo. Feels sluggish.

I just took the plugs out, regapped them a tad tighter (.29 or so) checked all connections into and out of blow valve and intercooler, tightened down both O2 sensors (NTK downstream O2 tightened a little bit more). Serpentine belt looks fine. I saw no obvious sign of exhaust gas leaks around the 02 sensors.

I need to drive the car and see how it feels and MPGs. My guess is that perhaps the NTK isnt giving the correct readings.
 

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You changed your O2 sensors due to regular maintenance correct and not due to the car not running right?

I had changed my O2 sensors recently due to bad fuel trims. Also my purge valve got contaminated due to all the extra fuel that was being dumped. You could also replace your purge vave. There like 25 bucks.

You could also recheck the connections for the second O2 sensor. Make sure everything is tight and nothing loose. Weird after the second O2 it is running sluggish. Nevermind just saw you had rechecked everything.

Double check you got the right part number for second O2. Pertty sure you got it right though.

Do you monitor your numbers?
 

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please awaken this older thread! presto-chango!

i am trying to unplug these connectors right now and finding it impossible.

I've got the battery box out, and can see the grey connector pretty well. the wires are too short to actually get it into easy view. But i *cannot* separate it. I know i'm going snap it in half if i keep jabbing a screwdriver in and hoping. and the black one i can see from beneath the car pretty well, but can't get that one either. any help for this meathead?

one last question - i've read that's theres' a fuse in the engine bay fuse panel that controls the heater on the front 02 sensor. nothing is labeled as such, altho there are several labeled "heat" . any help here?

thanks !
 

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please awaken this older thread! presto-chango!

i am trying to unplug these connectors right now and finding it impossible.

I've got the battery box out, and can see the grey connector pretty well. the wires are too short to actually get it into easy view. But i *cannot* separate it. I know i'm going snap it in half if i keep jabbing a screwdriver in and hoping. and the black one i can see from beneath the car pretty well, but can't get that one either. any help for this meathead?

one last question - i've read that's theres' a fuse in the engine bay fuse panel that controls the heater on the front 02 sensor. nothing is labeled as such, altho there are several labeled "heat" . any help here?

thanks !
it's in the manual i actually just checked this myself. it should be the fuses on the bottom of the box if you are standing in front of the car. i forget their numbers, i think 26, 28, 30?
 
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