[A4] Re: o2 sensor

Joel Landsverk jlandsverk at jjkeller.com
Fri Jul 23 12:29:16 EDT 2004

Most o2 sensor will come with a small amount of anti-seize already
applied.  Be careful to use an o2 sensor safe rust penitrant as well. 
It will state specifically that it is safe to use.

Good call on the daily applications for a week, and not an
overstatement in my experience.

'99 A4 1.8tq Avant
'96 A6 2.8q Avant 

>>> Kent McLean <kentmclean at mindspring.com> 7/23/2004 11:22:04 AM >>>
Richard Hurt wrote:
> What's the process for a 2.8 30v?

It's really quite simple.  In general, start at the engine's
exhaust manifold and work your way down to the tailpipe. You
are looking for electrical connectors coming out the side of
the exhaust. Look for one in front of the catalytic converter,
and one behind it. On a V6, you may have to repeat the process,
working your way down each manifold.

When you find an O2 sensor, disconnect the wiring, then unscrew
the sensor. You may want to use a special socket (17mm? 19mm?
3/4"? It will be labeled "O2 sensor socket".), available at
most auto parts stores. The socket will have a slit in the side,
to fit the wires.

Screw in the new O2 sensor, re-attach the wires, repeat for each
sensor you find, and you're good to go.

Some tips:

a) hit the O2 sensor with some good rust penitrant like PB Blaster
    (not WD-40), and let it work overnight. You may want to give it
    a spray every night for a week before you try to remove the
    sensor.  They can rust into place really solidly.
b) When the sensor is out, it wouldn't hurt to clean the threads.
    Someone said they're the same size as spark plug threads, so
    a "thread chaser" would be useful.
c) A dab of anti-seize might help the next time you need to do
    this, although some will argue that it may foul the new sensor.
    Use sparingly.

'94 100 S Avant, FWD auto
'89 200 TQ, "Bad Puppy"

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