How's this smog check result look?

[moribundman]

California emissons check; no dyno testing required for my car, due to AWD. Car's a '96 Audi A4 2.8l V6. Car has two cats and four O2 sensors. One post cat sensor was replaced about 60k miles ago, the other three are old. Car has a little over 130 k miles on the clock.

 

[brianl703]

The post-cat sensor has zip, zilch, nada to do with emissions. It's only there to make sure that the cat is functional. The pre-cat sensors are actually the ones that sense the air/fuel mixture.

 

[moribundman]

Yes, I'm aware of that. I don't know where I said the post-cat O2 sensor affected emissions? A defective post cat O2 sensor does however trigger a MIL and a code. The only reason I mentioned that one post cat sensor had been replaced was to stress the fact that the pertinent O2 sensors were 8 years and 130k miles old. Only one out of the four sensors, all of which are exactly identical apart from the lenght of the wiring harness, has gotten bad so far. That's all...

Now, what about my question?

 

[brianl703]

Post-cat sensors, in general, have a longer lifespan than do pre-cat sensors. So it is quite unusual that you would have had to replace a post-cat sensor before replacing a pre-cat sensor.

Although the sensors may be identical, they perform different jobs and are not subject to the same operating conditions, which results in the difference in their lifespan.

To answer your question, one of my vehicles (1996 Ford Contour 2.5L) has, at 97,000 miles, gone through the actual dyno test at 15 and 25MPH and produced CO of 0.03% and 0.04%, respectively. Also, HC ppm readings of 9 and 13, respectively. That is with new pre-cat oxygen sensors that I replaced due to a code (for one of them) and age (for the other).

So your results look good, but I wonder what they'd be if they could have done a dyno test.

 

[moribundman]

Well, dyno testing will become mandatory for even AWD vehicles in CA within a few years. Then I'll find out -- if my car is still around at that time.

By the way, back in '96 when I bought my A4, my second and third choices were the Contour SE and the BMW 318 Ti.

 

[brianl703]

I think Virginia is going to move to a scan of the OBD-II computer for '96 and newer vehicles, dropping the dyno or idle test for those vehicles.

Or maybe they'll do a scan AND a dyno or idle test.

If they just do OBD-II scanning just wait for the aftermarket to come up with "OBD-II simulators" which plug inbetween your existing OBD-II port and a new port and "sanitize" any trouble codes.

Oh, if anyone reading this decides to put this idea into production, you can send royalties to..

 

[moribundman]

I'm just glad the sniffer goes always in the correct tailpipe.

 

[Jimbo]

Great results. I notice they didnt test for NOX. Is that not required in your county?

Since the measured O2 was zero, the sensors are working fine, adjusting the mixture perfectly for the oxygenated California gas.

 

[brianl703]

NOx isn't tested on the two-speed idle test.

Only on the dyno...