Cleaning/testing O2's...

siege · May 31, 2004

Hey guys.

With the high gas prices lately I've gotten fed up with low gas mileage and decided I needed to figure out why. I've suspected my O2's so I just pulled them out to check them. is there any way to clean them up a bit or would it not help at all? just your basic brown carbon coating.

also is there a way I can test them to see if they're still good? and lastly, they are each different brands and styles. one is a bosch that is solid with a few vertical slits on it and the other is a denso that has like 4 rows of holes in it - would this affect anything? don't really want to start throwing parts at the thing since I am completely broke.

thanks

siege · May 31, 2004

well upon further inspection with a multimeter I found something interesting.

the bosch o2 has two white wires and one black. the denso has two black and one blue. the resistance between the two whites in the bosch is 4 ohms. the resistance between the two blacks on the denso is 16.5 ohms. does this have anything to do with anything or am I just barking up the wrong tree here?

sublime29 · May 31, 2004

Hello! I am not aware of a way to test them.That does not seem right though.Did you probe other ones to see if you can duplicate the 1st number.The plugs should go on one way to the engine harness.Look at the end of te O2 sensors an see if the colors do mean same wires on each sensor.There is no left and right so one is bad if they are the same wires you are touching. Later Sub

cjones · May 31, 2004

the best way to test O2s are in the car with the engine running. after the engine is warm the sensors should bounce between .2v and .8v. they should cross .5v atleast 2 times in 10 seconds.

the only way of cleaning them that i know of (that won't ruin them) is: with the sensor in the car. disconnect the sensor and hold the signal wire with one hand and touch the positive battery terminal with the other hand for a few seconds. your body's resistance droppes the voltage low enough that it won't harm the sensor but will burn off some of the deposits.

siege · May 31, 2004

sublime29 said:
Hello! I am not aware of a way to test them.That does not seem right though.Did you probe other ones to see if you can duplicate the 1st number.The plugs should go on one way to the engine harness.Look at the end of te O2 sensors an see if the colors do mean same wires on each sensor.There is no left and right so one is bad if they are the same wires you are touching. Later Sub

yeah the colors are in the same position on the connectors...the two blacks are in the same spot as the two whites. I cannot measure a resistance between any of the other wires.

cjones, which wires am I testing for voltage with the car on?

siege · May 31, 2004

by the way, the ones I tested resistance on were the two parallel to the flat side of the connector if anyone wants to check for me

jrichker · May 31, 2004

The following is a Quote from Charles O. Probst, Ford fuel Injection & Electronic Engine control:
"When the mixture is lean, the exhaust gas has oxygen, about the same amount as the ambient air. So the sensor will generate less than 400 Millivolts. Remember lean = less voltage.

When the mixture is rich, there's less oxygen in the exhaust than in the ambient air , so voltage is generated between the two sides of the tip. The voltage is greater than 600 millivolts. Remember rich = more voltage.

Here's a tip: the newer the sensor, the more the voltage changes, swinging from as low as 0.1 volt to as much as 0.9 volt. As an oxygen sensor ages, the voltage changes get smaller and slower - the voltage change lags behind the change in exhaust gas oxygen.

Because the oxygen sensor generates its own voltage, never apply voltage and never measure resistance of the sensor circuit. To measure voltage signals, use an analog voltmeter with a high input impedance, at least 10 megohms. Remember, a digital voltmeter will average a changing voltage." End Quote

Measuring the O2 sensor voltage at the computer will give you a good idea of how well they are working. The computer pins are 29 (LH O2 with a dark green/pink wire) and 43 (RH O2 with a dark blue/pink wire). Use the ground next to the computer to ground the voltmeter.

The O2 sensor ground is in the wiring harness for the fuel injection wiring. I grounded mine to one of the intake manifold bolts

eagle87 · May 31, 2004

Then if you drive the car with the meter connected off of the computer RH or left HEGO and you read anything from .7 and up and you have no top end with bad fuel economy your pig rich and have a problem. is this correct....

siege · May 31, 2004

hmm here's an idea! make sure they're both plugged in ALL THE WAY seems that the connector on the pass. side is a little finicky and it takes some effort to get it plugged in all the way. when I removed the O2 I kinda grabbed the connector and it just slid right out of the socket with no effort, but the driver's side one took some work. as I was putting them back in, I kinda wiggled the pass. side and it went in a lot more and clicked and now it takes some muscle to get it out....so it seems as though the people that put that O2 in before (a shop did it once, and a mechanic friend did it again when I swapped my off road H back in) didn't get it plugged in.

I just got back from test driving and I can't really tell if its my imagination or what, but I seem to be chirping the tires a lot now and when I got back, there is no gas smell coming from the motor - hoorah. that combined with cleaning out the IAB (it was horribly dirty) and removing the power steering and draining the fluid from the rack (which kinda sucks btw) made a world of difference.

haven't even tested the O2's yet - not even sure if I need to - but I probably will later today. Thanks guys

...I hate it when its always the stupid solution
"It doesn't work." "Is it plugged in?"
bah!

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