O2 Sensor Problem?

[old929guy]

89 HC US model 67,000 miles
A little history, had to remove and replace heads, had a water leak afterwards not sure from where but suspect the intake manifold gasket area. Used www.stealseal.com to fix leak (it worked).
Been driving about 2000 miles since fix. Going to work CEL came on, then went off. Driving home CEL came on again and went off again. I pulled a code 17 out of the computer. Reset the CEL and using the manual did some debugging. CEL came on again but with a code 15 this time. All of this relates to the o2 sensor and a couple of other things. I'm thinking I may have comtaminated the sensor if anti freeze was being sucked in although I do not get ANY smoke out of the tailpipe but maybe before I used the sealer I might have contaminated the thing. Also, maybe the sealer itself screwed things up although I wonder since it too so long for the CEL to be thrown. I did remove the O2 sensor when I was doing the engine work and just put it back in. Does it seem likely that the failure is in fact the O2 sensor? My other 929 same year w/157000 miles has the original sensor in place, no issues. Would the O2 sensor have a look, like greenish or whatever if anti freeze got to it? Do they just sometimes fail just for the **** of it? I found a good replacement for about US$53 but don't want to be wasting my money if in fact I need to take this friggen motor apart again.

Any O2 experiences/problem information appreciated.

[Matsuda 9]

pull out the sensor, if its covered in white dust then your coolant got to it and you should replace it. if its gunky and wet, then oil/too rich mixture. it should be replaced.

there was an NGK poster floating around the net about how to read O2 Sensors, similar to NGK how to read spark plugs. google it, should be easy to find

[mazdaspeed929]

Check it like Matsuda 9 said. That way you to diagnose the problem better if you know the situation with the O2 sensor.

If the sensor got knocked up during the removal that could have messed it too, some of them are vary fragile.

[Matsuda 9]

here you go:

How can I test an oxygen sensors performance to know if it needs to be replaced?

On Car Test - Before you can test the operation of the sensor, you will need an oscilloscope. You should first check that the basic engine set up is to the manufacturers’ specification, then thoroughly warm up the engine - remember that the sensor will only function once it has reached its operating temperature.

Two methods of testing an oxygen sensor are using an oscilloscope or a multimeter. An oscilloscope is the best method for testing. This will give you the exact output of the sensor along with its response times. A multimeter can also be used but this will only give an indication if there is an output or no output. The sensor will be switching too quickly for any response times to be measured.

OSCILLOSCOPE - Using an appropriate connecting device, connect the sensor output to your oscilloscope; do not disconnect the sensor from the ECU. Run the engine at approximately 2000 rpm. A properly functioning oxygen sensor will show a rapidly fluctuating output voltage between approximately 0.1 and 1.0 volts. The time taken for the voltage to change from 0.1V to 1.0V (referred to as the lean to rich response time) should be about 300 milliseconds. A similar time should be measured when the voltage changes from 1.0V to 0.1V (rich to lean response time).

MULTIMETER - For testing with a digital multimeter you will also need to connect the sensor output to the multimeter using an appropriate connecting device. Run the engine at approx. 2000-2500 rpm. The output will be a DC voltage, oscillating between approximately 0.1V and 1.0V. Although the sensor output is technically an oscillating DC voltage, some multimeters may require to be set on AC voltage measurement to correctly read the sensor output. Also, the response time of the multimeter must be better than the response time of the sensor. If the multimeter is too slow, then a constant output will result, even though the sensor is actually switching.

If the sensor output is constant or the response time is too slow, the sensor should be changed. It is a good idea to check the oxygen sensor function at every tune up and before submitting cars for emission tests. A slow sensor will affect fuel economy. A new sensor will pay for itself by cutting fuel bills.



source: www.ngk.com




good reading:

http://www.ngk.de/Lambda_sensors.681.0.html



Catalog:

http://www.ngkntk.co.uk/working/FileLib/La...20Catalogue.pdf

Application - Crossreference - and some good reading

[old929guy]

Thanks Guys, great info. Ordering the replacement today. I remember when I had it out during the engine teardown that it looked kind of whiteish. I'm going to try the test with a multimeter. It's a DVOM so I hope it'll be quick enough to watch the voltage. Regardless, I am going to replace the thing. Light didn't come on this morning and to me that sort of signals it's not totally crapped out but is borderline.

[sim_rx3]

as a rule of thumb the sensor should be replaced every 40,000km's