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O2 sensor replacement - final report
Posted 28 September 2002 - 11:23 AM
Posted 28 September 2002 - 11:25 AM
Posted 28 September 2002 - 11:35 AM
Had a film of black soot in the tail pipe for the last six months and diminishing fuel mileage performance.
Replaced the O2 sensor with an universal one Standard Motor Products SG 36. 83$ CAN. Have to splice the new sensor to the previous wires and connector. Old sensor was a Bosch LSH 24.
1) I was able to work from above. I bent over the passenger side fender and worked with an 11 incb long 22 mm open end wrench. The sensor is reached just behind and below the pass side half shaft inner boot. Very easy compared to what I had to go through with my old Loyale (under and the sensor still hard to get at and work on).
2) Results: silk smooth idle and what seems like better acceleration (not absolutely sure of that since I rarely put my foot to the floor).
3) Not driven enough to measure imporvement in fuel mileage yet. But i got 15.5 miles a US gallon for the last 121 kilometers (stop and go city driving and short distances) before the sensor replacement. I EXPECT improvement. Will report back.
ONE LAST THING: I was surprised to find the old sensor tip relatively clean and with a ligh tan color similar to what a spark plug looks like when evey thing is fine in the related cylinder. Black soot in the tail pipe but not on the sensor!!??
Posted 28 September 2002 - 11:36 AM
Posted 29 September 2002 - 05:35 PM
Posted 30 September 2002 - 09:46 AM
Idle speed also came back to the standard value of 700 rpm after having been 50 to 75 rpm lower since the beginning of summer.
Posted 02 October 2002 - 05:44 AM
Posted 02 October 2002 - 10:24 AM
When I replaced it on my former Loyale, I had all kinds of improvements and had gotten no CEL.
I think this is true for the front O2 sensor which monitors the air fuel ratio. My opinion is that the rear one should only be replaced when it triggers a CEL. All it seems to do is monitor the effectiveness of the Catalytic converter. Relacing it before it triggers a CEL would serve no purpose.
Not replacing the front one in time and driving with an overly rich mixture (dont know why a tired O2 sensor seems never to produce too lean a mixture) can shorten the life of the cat, wash off the protecting oil film on the cylinders walls, contaminate the oil and cost you for unnecessaryt fuel.
Posted 04 October 2002 - 07:58 AM
1) No more soot in the tail pipe
2) Smoother idle. A bit faster also.
3) Better fuel mileage: 14 liters for 100km instead of 15.5 before the replacement. City driving, stop and go, short distances.
4) Maybe better acceleration, but not absolutely sure of that.
5) Not very expensive: around 50$ US for a universal one.
6) Able to make replacement from above on 96 Legacy = very easy. Details on former post.
Hope that can help someone.
Posted 04 October 2002 - 02:27 PM
Posted 08 October 2002 - 06:32 AM
Sometimes you can test their output. Using a high impedence meter (usually any digital meter), read the signal wire. 2 wire and 3 wire units are 'self heating' the 2 wire has a signal and a power wire for the resistive heater. 3 wire units include a ground. The signal should be 0-1 V DC and when hot (they aren't used when the engine is cold) and stay very near some set value (0.45, 0.5 0.55V DC or thereabouts). The fuel injection computer should manipulate the injectors for the right mixture about as fast as most meters are. So you shouldn't see much if any variation on your meter.
Posted 08 October 2002 - 11:21 AM
I suspect that what happens to a tired sensor is not so much that it's output range is diminished (at both ends or at one of them) but that the rate at which it reacts to change in the oxygen content of the exhaust gets slower and slower. I'm not sure the test you're referring to would spot that.
All I know is that the real time data on the sensor provided by my OBDScan from Harrison did'nt detect anything wrong with the volt range of the sensor (it does'nt give a mean value but follows the volt output fluctuations of the sensor (hard to read with normal eyes, but you can detect the max and min value. That's why I propose to rely mainly on easy to spot symptoms to diagnose an out of spec sensor that has not triggered a CEL yet.
This is of course nothing but a mixture of experience, theory and opinion on my part.
Posted 11 October 2002 - 01:00 PM
The range doesn't change (0-1 V DC), but the speed of the output does. I wasn't at all clear.
I still think looking at the output on a digital meter can help assure a proper diagnosis. A good sensor should be acting in nanoseconds, a bad sensor in milliseconds.
Posted 22 October 2002 - 01:54 PM
I just checked at my dealer here in Europe 1 Subaru O2sensor costs $220 !
Might get one from the us? (I have 96 Outback)
Big issue here is the MAP sensor. The dealers are replacing those because they seem to 'wear' without triggering a check engine light. Same anywhere else?
Posted 23 October 2002 - 06:26 AM
How do they compare to the OEM one? I don't know. I just presume they are made the same way.
Posted 24 October 2002 - 11:52 AM
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