Quote:
Originally Posted by ILUVMILS
Don't worry about the wave-form. The thing you need to check is how the sensor responds to a lean condition. The test is quick, simple, and conclusive. All you need to do is monitor the sensor voltage. With the engine at operating temperature, hold the RPM at around 2,500. Wait until the voltage oscillates normally, then floor the accelerator for a split second and lift off. This will instantly trigger "decel-shut-off" (about as lean as it gets). The sensor voltage should drop like a rock. A healthy sensor will drop all the way to zero. Try this and post the results.
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I had some free time today and generated the following results:
Using the test above I was able to get my 02 sensor voltage to drop to about 10-15 mv. In the first test it will drop to about 20-25mv and subsequent tests produce lower results - after 5 or 6 tests I'm getting down to about 10-12mv. It doesn't seem to go any lower than that no matter how many times I try the test. It's amazing how fast it drops, watching the pattern on the scope it falls pretty much instantaneously and holds lean for 3-4 seconds then switches back to rich for 2-3 seconds before stabilizing back to a sine wave pattern.
20-25mv isn't zero mv but it doesn't seem too bad, do you think its high enough to cause a problem?
I also spent more time looking at the actual waveform and it seems to be a bit lazier than I remember it being...... the sensor oscillates from lean->rich/rich->lean about 0.8 times per second. Sample 02 traces that I've seen seem to indicate it should oscillate 3-5 times per second.
If I increase the RPM to 2K (and presumably the temperature of the sensor) it will oscillate about 2 times per second. Looks like the hotter my sensor is the better it seems to perform.
Thanks - Tim