O2 sensor


Dangeranger3

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1999 Explorer 4.0 Passenger after cat O2 sensor is bad but I can't get it out for the life of me!!! I remember reading letting the exhaust warm up a little bit will help but does anyone have any other tips? I can't get a good swing at the wrench with a hammer even with a block against it. And now the bolt is starting to round off. Any ideas at all would be appreciated. Thanks.
 


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NVR2FST

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I just went through this today...I kept soaking it and heating it (red hot), put a 1/2" ratchet on it with a pipe and pulled like crazy. Just make sure you use an 8pt socket (I cut off the pig tail and enough of the old sensor to fit the socket). Several hours later I got it out. Good luck!
 

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i have seen them in specialty uses but don't remember what it was .aircraft maybe?
 

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There is a special oxygen sensor socket around, that has a slot in it for the pigtail.

Having said that, you can use a box end wrench or flare nut wrench as well. Do NOT use an open end wrench. Cheater pipes help.

I don't think I've ever seen a bad downstream HEGO sensor. A code there usually means the cat is ineffective or there is an electrical problem. Anything that might foul the downstream sensor is going to hit the upstream sensor worse.
 

homeless69

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MAKG,
Since we are on the 02 sensor topic maybe you could help out here. I had pulled a code for the 1st bank sensor, replaced it and the engine still hesitates but not as much as before, would it have been a good idea to replace both upstreams instead of just the replacing the one? Wondering what your thoughts on this might be.
Thanks again.
 

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If it ain't broke, don't fix it.

And most (though not all) HEGO sensor codes aren't due to HEGO sensors. No code authoritatively condemns any sensor, and you can very easily flip lean codes by misfiring one cylinder (among quite a few other potential causes).

HEGO sensors do eventually get consumed, but not ANYWHERE NEAR as quickly as people seem to think. I've got two original fully functioning oxygen sensors in my Prizm with it's 265,000 miles. Almost all oxygen sensors are the same, aside from mounting details, how the sensor is grounded, and whether or not it is heated.
 

Dangeranger3

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I got the sensor off with the wrench (not the open end) I think letting it soak in PB overnight and a little massaging from the BFH helped out. FWIW autozone does have the special socket that you can just borrow. I think it would have made the job easier from the beginning. Also, the sensor did look slighly fouled and was full of white buildup in one of the slots which air enters. So hopefully this fixes the problem. And the CEL has to be reset correct? Thanks for the help.
 


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