Changing right pre cat O2 sensor....

[jbriner1]

I found an interesting tool at Auto zone that made changing this sensor a little easier... it's called a crows foot sensor wrench. I used this wrench, a swivel head ext, a 10 inch ext bar, and an 18 inch breaker bar and managed to loosen this sensor enough to work my hand in (over the top of the motor, arm parallel to firewall) and unscrew it by hand. The 18 inch breaker bar is not a necessity, but the 180 degree swivel head on it is... so if you have a swivel head ratchet this is probably better. All of these hand tools are 1/2 inch drive.With my index finger hooked thru the drive portion of the crows foot wrench I ran my hand/arm parallel to the engine from the front and placed the wrench over the sensor. The swivel head extension, 10 inch ext are connected and dropped down to the c.f. wrench and then breaker bar is attached. The extension are snaked down where the 2 heater hoses join the fire wall and what look to me like brake lines. (I don't know what they are.) You can tell where to snake it through by looking at where and how the c.f. wrench is sitting. Basically, you are doing 1/4 turns or less at a time before you have to reset the c.f. wrench, but it works. I accidently ordered the wrong sensor... pre as opposed to post cat.. was replacing the post cat and thought I would give this wrench a try on the pre cat and it worked. Though I might pass it on since I've read that the pre cat O2 sensor is a nightmare to change. This wasn't too terrible. Good luck.

[timmack]

nice post, thanks for the good info.

[99QX4]

Very interesting, and will probably come in handy considering i found out today that i need to change one too!

[SnowSurfLax]

Pics! Pics!

If you didn't take any, keep it in mind for future reference.

Do bad O2 sensors always throw a CEL?

[pathfinder_top_gear5]

^^ yes

[tmorgan4]

There's also a "special" O2 sensor socket with a cutout for the wire to run though.

If anybody wants some O2 sensors I've got 4 that didn't throw any codes (2 pre-cat, 2 post cat).

[nissandoms47]

Sometimes a bad 02 sensor will throw an SES light but sometimes it wont and you'll just get terrible gas mileage.

[voolover]

As opposed to great gas mileage.....?

[gwhunt23]

As opposed to great gas mileage.....?

Yes, before my O2 sensor went I got about 21mpg on the highway. With a bad O2 sensor, I would get about 12-13mpg.

[GotDirt443]

i think my O2 sensors are shot... when coldstarting my Qx4 until it warms up a nice oder of gas is in the air, like it is running really rich and spuing out unburned gas... whats th fastest way to check them???

[tmorgan4]

i think my O2 sensors are shot... when coldstarting my Qx4 until it warms up a nice oder of gas is in the air, like it is running really rich and spuing out unburned gas... whats th fastest way to check them???

That is normal. The engine runs in "open loop" mode where it doesn't rely on feedback from those sensors until it reaches operating temp. It always just runs super rich when it's cold out to warm up and improve idling.

[jbriner1]

hey all, glad I could help... now, if someone could tell me how to post some pix... I took a few of tools that I'm talking about. I tried w/ the socket with the wire cut out, but on some of the Bosch sensors, the socket would not sit all the way down, that's when I discovered the crows foot wrench. It's a bit of a pain to get my hand in there.. I came away w/ a few sore spots and skinned areas on my hands and arms, but once again, it wasn't terrible.I'm new to forum stuff so I have no idea how to post pix.thanks


Modified by jbriner1 at 10:25 PM 2/10/2008