PC2

I am relieved and glad that I passed the dreaded California SMOG TEST today. My car was assigned to a Test Only center which tests "gross polluters". Everything checked out fine with the following results:

15MPH (RPM 1617) (%CO2 14.0) (%O2 1.4) (HC 30) (CO% 0.08) (NO 441)
25MPH (RPM 1681) (%CO2 14.0) (%O2 1.1) (HC 24) (CO% 0.07) (NO 520)

All measurement were below average except for NO levels. The average was 237 for 15MPH and 199 for 25MPH. My measurements were about 50% above average but still below maximum allowable (785 for 15MPH, 724 for 25MPH). Anyone know if it's because the CAT is getting tired?

Kahdmus

Congrats Peter!! :-)

Dave R.

Perhaps your Oxygen sensor is getting tired?

The engine cycles between slightly rich and slightly lean so the cat can do its thing, as oxygen sensors age they respond more slowly and also start to indicate leaner than actual (thus causing the engine to run rich)

pete000

Gotta love LA

PC2

Dave, Do you know what is the life span of the O2 sensors?

garrett376

Peter - why were you worried about the car not passing? Did it fail previously?

I think Adrian's book covers testing your O2 sensor to see if it is still in spec.

PC2

Garrett,

According to DMV, my car had passed all previous tests. But this time I was just a bit paranoid because I discovered, after 15,000 miles + 2 DE events later, that 1 & 4 plug wires on the primary distributor were mixed up (Ok, I'm publicly confessing I'm a idiot). I had thought the O2 sensor and CAT would have been damaged by the unburned fuel but the smog test proved otherwise. I'm just hoping the engine is not severely damaged. I'll probably change out the O2 sensor when I do my 60,000 service.

Arjan B.

Pete, congrats......... but you know as much as we do that is never will be much of a problem to have the good data during the test.

The 02 sensor can last long. In my experience most of the time the Cat. converter fails . We replace not that much )2 sensors, only if a fault code is availible. I would check for a rebuild cat if I was you Pete, much cheaper.

PC2

Thanks Arjan, I was thinking of replacing the old CAT with a high flow model. I found a supplier that makes high flow CAT in the exact shape and size of the OEM. And the price is half of the new one ($385).

Dave R.

Peter,

I don't know how long oxygen sensors last and I don't know if yours needs replacing - you did pass emissions, after all.

Steve Weiner seems to think 60k miles is a reasonable replacement interval, see for example this thread. Others (e.g. Arjan) have a different viewpoint.

I changed out my Osensor because I was curious to see if it would make a difference and was glad I'd done so when I saw the condition of the wiring on the old sensor - insulation was broken on one of the wires and the conductor was corroding through. I've not yet checked for any difference in fuel consumption, and I've been working through other sources of driveability problems (caps & rotors, ignition wires, coils all replaced... ISV & air flow meter yet to be cleaned) so I don't know if the new Osensor is performing better than the old one.

Arjan's suggestion of swapping out the cat is reasonable, but I think here in the states it is illegal to swap in a used cat? Although if swapping in an old cat solves emissions problems who cares... New cat would be expensive.

www.thepartsbin.com sells OEM oxygen sensors for about $110 (complete with rubber grommet bearing a Porsche part number, 928.XX... and protective sheath), that's where I got mine - select it from the parts menu for your specific car, e.g. this link not from the oxygen sensor sub-site. My new Osensor came with a protective sheath over the wires between the sensor and the rubber grommet, just like the old one, and I pulled/pushed the sheath down over the back end of the sensor to prevent water from entering the wire paths into the sensor.

PC2

Dave,

Thank you for the reply. Although I passed SMOG, I'm a bit concerned of the high level of NO measurements. Especially after I discovered the mixed up wires on the primary distributor. I'm debating if I should just leave it until it fails or just replace the O2 sensor & CAT all together as a part of the 60,000 miles maintenance that is coming up. I would be curious to know if your O2 sensors make a difference. Please keep me posted.



PS. Thanks for the link to the O2 sensor, it is one of the better prices I've seen.

joey bagadonuts

Congrats, Peter!

This item might not be a cat replacement but rather, a cat bypass pipe. Most of the high-flow sport cats I have come across run from $800 - $900. Also, I recall hearing that these 100 - 200 cell cats do not last as long as the stock part (something else to worry about ).

$0.02

garrett376

and do you think that a sport catalytic converter does enough "cleaning" to pass smog? Know anyone who has passed with one of those? I'd be afraid to try now that the smog check stations transmit the smog results immediately - would hate to be labeled as a "gross polluter" - that happened with my Datsun 240Z a while back! That stunk! (pun intended!)

PC2

Thanks Joey!

I was a bit skeptical about the product mainly because of the low price. But after further reading of the info on their web site, I found their cat meets both EPA & CARB requirements. But your point of the 100-200 cell cats not lasting long is interesting. Here's the web site if anyone is interested. http://members.aol.com/SportsCarConvert/index.html

garrett376

Thanks for the link - I will save that one... it looks promising! Get one and let us know if you pass smog!!!!