O2 sensor on 2002 Legacy

[Cliff Top]

Hi chaps,
I posted last week regarding loss of power and poor economy.

I had the car checked at a dealers and there are no error codes or anything
obviously wrong. They suspect it may be a problem with the O2 sensor even
though the ECU hasn't logged a code. They also suggested it may have been a
bad batch of supermarket petrol that has somehow contaminated/coated the
sensor so that it isn't reading correctly, hence the wrong mixture and poor
economy/performance.

Has anyone encountered this coating problem before... and does it clear? or
can it be cleared by say a strong injector cleaner mixture. I have so far
used 4-5 tanks of fuel since the problem occurred and it hasn't
improved..... it hasn't got any worse either which I might have expected if
the senor itself was gradually failing. What symptoms do you get with a
faulty/failing O2 sensor?

Thanks for any help

Cliff

 

[Carl 1 Lucky Texan]

Hi chaps,
I posted last week regarding loss of power and poor economy.

I had the car checked at a dealers and there are no error codes or anything
obviously wrong. They suspect it may be a problem with the O2 sensor even
though the ECU hasn't logged a code. They also suggested it may have been a
bad batch of supermarket petrol that has somehow contaminated/coated the
sensor so that it isn't reading correctly, hence the wrong mixture and poor
economy/performance.

Has anyone encountered this coating problem before... and does it clear? or
can it be cleared by say a strong injector cleaner mixture. I have so far
used 4-5 tanks of fuel since the problem occurred and it hasn't
improved..... it hasn't got any worse either which I might have expected if
the senor itself was gradually failing. What symptoms do you get with a
faulty/failing O2 sensor?

Thanks for any help

Cliff

Are they guessing or have they measured the operating voltage range of
the sensor?

Carl

 

[Ray]

Hi chaps,
I posted last week regarding loss of power and poor economy.

I had the car checked at a dealers and there are no error codes or anything
obviously wrong. They suspect it may be a problem with the O2 sensor even
though the ECU hasn't logged a code. They also suggested it may have been a
bad batch of supermarket petrol that has somehow contaminated/coated the
sensor so that it isn't reading correctly, hence the wrong mixture and poor
economy/performance.

fwiw, when the front 02 went on my 02 legacy, the problems were:
CEL came on, with 02 sensor errors (P0130 IIRC) and fuel trim issues and
misfire issues.
Car ran fine when cold, but would idle like crap when warm and would
feel "jerky" once in a while under power, but was fine at WOT.

I'd suggest finding a real mechanic to hook up a real scan tool to it.

Ray

 

[Cliff Top]

Are they guessing or have they measured the operating voltage range of
the sensor?

Carl

I think they are just guessing rather than having actually measured x
microvolts output. To be fair they didn't want to change the sensor yet ,
instead suggesting wait and see if the CEL light eventually comes on and
read the error code.
As a tv engineer etc and having plenty of test gear, I wondered if it would
be possible to check for myself the output of the sensor, but would need to
know what readings to expect and under what conditions.
They have just hooked up and seen no error codes and given a few other quick
checks come to the above conclusion.

 

[Carl 1 Lucky Texan]

been a



I think they are just guessing rather than having actually measured x
microvolts output. To be fair they didn't want to change the sensor yet ,
instead suggesting wait and see if the CEL light eventually comes on and
read the error code.
As a tv engineer etc and having plenty of test gear, I wondered if it would
be possible to check for myself the output of the sensor, but would need to
know what readings to expect and under what conditions.
They have just hooked up and seen no error codes and given a few other quick
checks come to the above conclusion.

If you have a wide-band sensor(not sure when soobs got 'em), I think it
should be around .45 volts output.

http://www.megasquirt.info/PWC/LSU4.htm

or google up some info or find a Haynes manual.

Carl

 

[Cliff Top]

If you have a wide-band sensor(not sure when soobs got 'em), I think it
should be around .45 volts output.

http://www.megasquirt.info/PWC/LSU4.htm

or google up some info or find a Haynes manual.

Carl

Thanks for the input so far...I'll research more on the sensor operation.
0.45v output - for correct O2 /mixture reading?
Measured on which of the sensor pins... any idea?

cheers Cliff aka Andrew

 

[Carl 1 Lucky Texan]

Thanks for the input so far...I'll research more on the sensor operation.
0.45v output - for correct O2 /mixture reading?
Measured on which of the sensor pins... any idea?

cheers Cliff aka Andrew

Try asking over at www.ultimatesubaru.org . I know a poster called
Legacy 777 has extensive number of photos he shares on differnt problems.

Carl