is there way to clean o2 sensors?
03-18-2007, 09:46 PM
#11
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RE: is there way to clean o2 sensors?
Is it still 1v??
Essentially, it's a thermometer, that interprets high temps to a lean condition, and cooler temps to a more rich situation, w/ in reason?? Similar to the MAF (Except for air count)??
JT
Essentially, it's a thermometer, that interprets high temps to a lean condition, and cooler temps to a more rich situation, w/ in reason?? Similar to the MAF (Except for air count)??
JT
03-18-2007, 10:02 PM
#12
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RE: is there way to clean o2 sensors?
Temperature of the exhaust gasses is only related to the extent that the sensor needs to be hotter than 662°F to work at all, and 950°F or better to work optimally--here's a link to more than anyone probably wants to know about PZ O2 sensors...[/align][/align]It is the voltage differential generated by a catalytic reaction of two permeable platinum electrodes and the oxygen content of theirenvironments.One electrode is exposed to atmospheric air and serves as a reference,the other is exposed to the exhaust gasses--the catalytic action between the heated platinum electrodes and the differing O2 content of the environments produce different voltages, it is the difference between these which is the sensor's output.[/align][/align]And undecided.steve correctly pointed out, as the platinum electrodes experience physical wear the catalytic reaction can get "sluggish" after extended use--this sluggish behaviour often triggers the "slow response" DTC.[/align]
03-19-2007, 10:02 AM
#13
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RE: is there way to clean o2 sensors?
ORIGINAL: cliffyk
A PZ (platinum/zirconium)O2 sensor produces no output waveform, it simply produces an voltage related top the oxygen content of the exhaust gasses--the waveform (usually 0.5 to 5 Hz) seen on a scope on an operating engine is a result of the EFI computer's closed-loop dithering the fuel mix around the stoichiometric point* to achieve and average mixture of 14.7:1.[/align][/align]The propane torch test is a very accurate method for testing PZ sensors, you are actually measuring the O2 content of the blue inner flame--I have verified (good or bad) at least 40 PZ sensors using this method over that last 20 years, those that passed this test were OK (assuming the heater was also good). [/align][/align]However, to be perfectly honest most of these tests were done back when replacements cost 2 to 3 times what they do now (relative to the CPI)--they are cheap enough now, and the diagnostic tools are much better, that if the tests point to a bad sensor I just slap one in...[/align][/align]----------------------------------[/align]* - More correctly, the ECU's dithering of the mix to produce an average A/F ratio of whatever it wants for the given closed loop conditions, as lean as 16:1 to 17:1 at light loads for best economy, and as rich as 13:1 to 12:1 at higher loads but still in closed loop.[/align]
A PZ (platinum/zirconium)O2 sensor produces no output waveform, it simply produces an voltage related top the oxygen content of the exhaust gasses--the waveform (usually 0.5 to 5 Hz) seen on a scope on an operating engine is a result of the EFI computer's closed-loop dithering the fuel mix around the stoichiometric point* to achieve and average mixture of 14.7:1.[/align][/align]The propane torch test is a very accurate method for testing PZ sensors, you are actually measuring the O2 content of the blue inner flame--I have verified (good or bad) at least 40 PZ sensors using this method over that last 20 years, those that passed this test were OK (assuming the heater was also good). [/align][/align]However, to be perfectly honest most of these tests were done back when replacements cost 2 to 3 times what they do now (relative to the CPI)--they are cheap enough now, and the diagnostic tools are much better, that if the tests point to a bad sensor I just slap one in...[/align][/align]----------------------------------[/align]* - More correctly, the ECU's dithering of the mix to produce an average A/F ratio of whatever it wants for the given closed loop conditions, as lean as 16:1 to 17:1 at light loads for best economy, and as rich as 13:1 to 12:1 at higher loads but still in closed loop.[/align]
heres also a good read....
http://www.babcox.com/editorial/ic/ic10044.htm
.
03-19-2007, 10:43 PM
#14
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RE: is there way to clean o2 sensors?
A DSO certainly makes it easier to diagnose a sluggish O2 sensor, however I think you'll agree that most DIYers do not have or even have access to such instruments (I actually havetwo, a Lecroy 9450Aand a Tek 2430--but I'm an admitted nut case).[/align][/align]In the absence of a DSO, the propane torch test (when properly conducted) will reveal the respone speed of the sensor within acceptable limits.[/align]
03-20-2007, 03:36 AM
#15
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RE: is there way to clean o2 sensors?
ORIGINAL: cliffyk
It is the voltage differential generated by a catalytic reaction of two permeable platinum electrodes and the oxygen content of theirenvironments.
It is the voltage differential generated by a catalytic reaction of two permeable platinum electrodes and the oxygen content of theirenvironments.
One electrode is exposed to atmospheric air and serves as a reference,the other is exposed to the exhaust gasses--the catalytic action between the heated platinum electrodes and the differing O2 content of the environments produce different voltages, it is the difference between these which is the sensor's output.
I'm very interested in learning this, and that's why I'm asking
JT
03-20-2007, 10:40 PM
#16
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RE: is there way to clean o2 sensors?
Forget temperature. Other than that the sensor has to be at least 660°F (950°F+ for optimal operation), temperature has nothing to do with a narrowband sensor's operation.[/align][/align]There is a small port in the sensor body (filtered via a heat resistant method) that allows atmospheric air to enter the inner cone of the sensor--it's referenced as "Porous PTFE Filter" in this (click here)cutaway drawing from Nippon-Denso. It's also shown in this more stylised drawing from Bosch. If you closely examione any PZ sensor you'll see the atmospheric ports, sonetimes a single hole at the end near the wire exit, sometimes a ring of holes around the heeet metal part of the body.[/align][/align]The sensor's output is the result an electrochemical process based upon the Nernst Principle (click-here to read about how PZ sensors work here). There is no additional input or sensor involved in the O2 sensor's delivery of a meaningful signal to the PCM, it's all quite self-contained.[/align]
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