post #1 of Old 09-14-2005, 01:07 AM Thread Starter
saxj
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Can you clean an O2 Sensor?

I know what an O2 sensor does, but have no idea how they work.

When an O2 sensor goes "bad" what happens to it?

How does an O2 sensor work?

Can you clean them or do they have to be replaced?


1996 Cherokee Limited 4x4
OME Springs, 30x9.5 M/Ts, 4.0 HO Auto, NP242
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post #2 of Old 09-14-2005, 03:28 AM
tigerpaw580
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O2 Sensor

The O2 sensor is very important to how your Jeep runs.It measures the oxygen in the exhaust and adjusts the pulse width of the injectors based on its signal.I have never seen one able to be cleaned. It is a easy replacement and just dont forget the anti seize lube on the threads, don't contaminate the tip any.
It is possible to test the o2 sensor with a digital voltmeter, check it it should read between 0.1 volt to 1.0 volts anything else and it is bad. You may also improve how your jeep's mileage is too by just replacing it, even if it is not bad yet.I have had good luck with the Bosch type sensor, just get the one with the correct terminal on the end not the universal. for either the 2.5 four or the 4.0 engine.
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post #3 of Old 09-14-2005, 07:35 AM
Jason, aka: Jeepin.com
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just replace it, they're relatively cheap.

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post #4 of Old 09-30-2005, 09:34 AM
maxpower_hd
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O2 Sensor

Where did you buy your O2 sensor? I just got a price and it was $80 for the upstream and $128 for the down stream. That doesn't sound relatively cheap to me.
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post #5 of Old 09-30-2005, 10:23 AM
xj-xile
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You can get them $60-$70 (each) on www.sparkplugs.com

I just bought them from the dealer $220.00 ($105.00 each, plus tax), thank you very much. So the $60 route is "cheap" in that sense.

Not that anyone cares, but I've been trying desperately to get a mechanic who will listen to me when I say my problem is not with the sensors, but with the wiring harness. The latest mechanic told me to buy the sensors from the dealer, because their tests told them that the Denso sensors I put on there were not communicating with the Jeep's computer. So I spend $220.00, right? And now, after installing them & resetting the computer, the bleeding CEL is back on...

...and my emissions inspection sticker expires at sundown today

So if anyone knows why the harness would be overloading (pumping too much electricity) into the O2 sensors, I'll take any suggestions. I measured the voltage coming from the harness to the sensors, & it seems too high, given what the FSM for a '94 XJ says (I don't have a '96 FSM, & note that a '94 is OBDI while '96 is OBDII).


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post #6 of Old 09-30-2005, 10:24 AM
XJ99
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I paid $90.00 each, and that was at the dealer.. I didn't think that was too bad for OEM parts..

When we do right, no one remembers. When we do wrong, no one forgets.
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post #7 of Old 10-01-2005, 11:06 AM
4SEVEN3
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Quote:
Originally Posted by xj-xile
So if anyone knows why the harness would be overloading (pumping too much electricity) into the O2 sensors, I'll take any suggestions. I measured the voltage coming from the harness to the sensors, & it seems too high, given what the FSM for a '94 XJ says (I don't have a '96 FSM, & note that a '94 is OBDI while '96 is OBDII).
The O2 sensor creates voltage. It uses voltage, but only for the heater is its a 4 wire sensor. If theres resistance between the sensor, like a bad pin in a connector, ect. and the ECU it can foul up readings. The best thing to do is using a oscilloscope take o2 voltage readings at the sensors plug and the ECU to see if theres any difference and trace it from there, take reading on the harness side of the connector for the o2 sensor. Maybe the computer is messed up?
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post #8 of Old 10-01-2005, 11:30 AM
dynamite44
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Quote:
Originally Posted by xj-xile
You can get them $60-$70 (each) on www.sparkplugs.com

I just bought them from the dealer $220.00 ($105.00 each, plus tax), thank you very much. So the $60 route is "cheap" in that sense.

Not that anyone cares, but I've been trying desperately to get a mechanic who will listen to me when I say my problem is not with the sensors, but with the wiring harness. The latest mechanic told me to buy the sensors from the dealer, because their tests told them that the Denso sensors I put on there were not communicating with the Jeep's computer. So I spend $220.00, right? And now, after installing them & resetting the computer, the bleeding CEL is back on...

...and my emissions inspection sticker expires at sundown today

So if anyone knows why the harness would be overloading (pumping too much electricity) into the O2 sensors, I'll take any suggestions. I measured the voltage coming from the harness to the sensors, & it seems too high, given what the FSM for a '94 XJ says (I don't have a '96 FSM, & note that a '94 is OBDI while '96 is OBDII).
the dealer kept feeding my jeep oxygen sensors, under warranty mind you, so after replacing sensor 1 upstream 3 times in a row (in i think 2 month's time), they rewired the engine bay, which solved the problem.

back to the subject stated earlier in the post:
i've heard of people cleaning oxygen sensors, in particular a couple of people when i worked the parts counter at pep boys. one redneck lookin guy tried cleaning his with gasoline, then turpentine. neither worked. the other guy that came in said he tried cleaning them with a wire brush, which also didn't help.
both customers wound up buying new oxygen sensors :-)
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post #9 of Old 10-01-2005, 03:23 PM
xj-xile
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Quote:
Originally Posted by 4SEVEN3
The best thing to do is using a oscilloscope take o2 voltage readings at the sensors plug and the ECU to see if theres any difference and trace it from there
You know, I wondered whether an oscilloscope would be more accurate/useful in this situation than a multimeter. I don't have an oscilloscope though... I know what the sensors are "saying," but I don't know what the computer is "hearing" (or reading) from the sensors.

If anyone really wants the nitty gritty I'm dealing with this in a different thread on NAXJA: http://www.naxja.org/forum/showthread.php?t=66704 I'm currently still stumped. It's either the computer or the wiring. It's not (in my case) the sensors.

re: cleaning O2 sensors: I believe I read that it is possible, some long time ago while trying to solve my problem. However it is done, it must be a delicate process. In most cases, though, if a sensor causes the Check Engine light to come on, then the sensor is probably broken, & cleaning it will not fix it. I also don't think cleaning it improves its efficiency.

Everybody should take a lesson f/what I did. If you don't have a Check Engine Light on DON'T MESS WITH THE SENSOR! If you're worried about the cost of replacing it, then you shouldn't be messing with it. I've bought three sets of sensors now for a problem that apparently has nothing to do with the sensors themselves, but everything to do with the wiring harness or the computer.


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