Post by eporter123 on Apr 1, 2008 22:38:49 GMT -5
Hey all,
I'm looking at my oxygen sensor as a possible cause for lowered fuel economy. Does anyone have a "Subaru Certified" measure for the voltage from a single wire O2 sensor?
This is for a 1990 MPFI Justy, but the numbers for a carb'd Justy can help future Justy owners who know how to use the search function of the forum! Feel free to post any O2 sensor knowledge here!
I read .40-.60 volt fluctuation online. I KNOW I read a similar number here on the forum, but after searching for half an hour, I've given up!
II was reading .25 or so. I may need to re-check that, but it was definitely not moving. The car had been sitting for a little bit after driving home though.
Anyways, hopefully some of you can expand on this topic.
From Autozone's 1985-1996 online service manual:
Single Wire Sensor
1.
Start the engine and bring it to normal operating temperature, then run the engine above 1200 rpm for two minutes.
2.
Backprobe with a high impedance averaging voltmeter or multimeter,set to the DC voltage scale, between the oxygen sensor (02S) and battery ground.
3.
Verify that the 02S voltage fluctuates rapidly between 0.40-0.60 volts.
4.
If the 02S voltage is stabilized at the middle of the specified range (approximately 0.45-0.55 volts) or if the 02S voltage fluctuates very slowly between the specified range (02S signal crosses 0.5 volts less than 5 times in ten seconds), the 02S may be faulty.
5.
If the 02S voltage stabilizes at either end of the specified range, the ECU is probably not able to compensate for a mechanical problem such as a vacuum leak, faulty pressure regulator or high float level. These types of mechanical problems will cause the 02S to sense a constant lean or constant rich mixture. The mechanical problem will first have to be repaired, then the 02S test repeated.
6.
Pull a vacuum hose located after the throttle plate. Voltage should drop to approximately 0.12 volts (while still fluctuating rapidly). This tests the ability of the 02S to detect a lean mixture condition. Reattach the vacuum hose.
7.
Richen the mixture using a propane enrichment tool. Voltage should rise to approximately 0.90 volts (while still fluctuating rapidly). This tests the ability of the 02S to detect a rich mixture condition.
8.
If the 02S voltage is above or below the specified range, the 02S and/or the O2S wiring may be faulty. Check the wiring for any breaks, repair as necessary and repeat the test.
I'm looking at my oxygen sensor as a possible cause for lowered fuel economy. Does anyone have a "Subaru Certified" measure for the voltage from a single wire O2 sensor?
This is for a 1990 MPFI Justy, but the numbers for a carb'd Justy can help future Justy owners who know how to use the search function of the forum! Feel free to post any O2 sensor knowledge here!
I read .40-.60 volt fluctuation online. I KNOW I read a similar number here on the forum, but after searching for half an hour, I've given up!
II was reading .25 or so. I may need to re-check that, but it was definitely not moving. The car had been sitting for a little bit after driving home though.
Anyways, hopefully some of you can expand on this topic.
From Autozone's 1985-1996 online service manual:
Single Wire Sensor
1.
Start the engine and bring it to normal operating temperature, then run the engine above 1200 rpm for two minutes.
2.
Backprobe with a high impedance averaging voltmeter or multimeter,set to the DC voltage scale, between the oxygen sensor (02S) and battery ground.
3.
Verify that the 02S voltage fluctuates rapidly between 0.40-0.60 volts.
4.
If the 02S voltage is stabilized at the middle of the specified range (approximately 0.45-0.55 volts) or if the 02S voltage fluctuates very slowly between the specified range (02S signal crosses 0.5 volts less than 5 times in ten seconds), the 02S may be faulty.
5.
If the 02S voltage stabilizes at either end of the specified range, the ECU is probably not able to compensate for a mechanical problem such as a vacuum leak, faulty pressure regulator or high float level. These types of mechanical problems will cause the 02S to sense a constant lean or constant rich mixture. The mechanical problem will first have to be repaired, then the 02S test repeated.
6.
Pull a vacuum hose located after the throttle plate. Voltage should drop to approximately 0.12 volts (while still fluctuating rapidly). This tests the ability of the 02S to detect a lean mixture condition. Reattach the vacuum hose.
7.
Richen the mixture using a propane enrichment tool. Voltage should rise to approximately 0.90 volts (while still fluctuating rapidly). This tests the ability of the 02S to detect a rich mixture condition.
8.
If the 02S voltage is above or below the specified range, the 02S and/or the O2S wiring may be faulty. Check the wiring for any breaks, repair as necessary and repeat the test.