O2 sensor removal

NANCY BAUER

MEMBER
1998 MERCURY MYSTIQUE
2.5L
6 CYL
2WD
AUTOMATIC
133 MILES

Have four O2 sensors on this, three were reasonably identified and able to replace by getting car up on ramps and getting dirty, but there is a fourth one that is buried up in the exhaust system. I was able to get it loose, but cannot get my hands up there in through the winding exhaust system. Do I have to drop the manifold down to get it off and replaced?

2 Replies

STEVE W.

MECHANIC
13,467 POSTS

Possibly, but if you managed to get it loose and can get it to fully back out you could probably use a magnet to get it the rest of the way out (or bribe a small handed child to remove it) The trick may be getting the electrical connector loose.
Why are you replacing them? Are they setting codes or causing problems?

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Sunday, December 4th, 2016 AT 4:26 PM

CARADIODOC

MECHANIC
33,873 POSTS

That was my question. There is no way four O2 sensors failed at the same time. With no symptoms listed, most people want to change sensors because they don't like the data they're providing. The best example is when an O2 sensor is reporting a lean condition and a diagnostic fault code is set related to that. A lean fault code can only be set by a properly-working sensor. Replacing the sensor won't fix the code. It's the cause of running lean that must be diagnosed and repaired.

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Monday, December 5th, 2016 AT 4:06 PM