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I recently had to go get my emissions done again before I could get my license tabs. Since the DOL puts the emission results on the Internet, I can easily compare the results from last week to when it was done in 2004. It seems my emissions have doubled since then, yet still passable. Is this a strong indication my cat is dieing?

It says there is left over oxygen along with the HC and my basic understanding of the system says the CAT is dying or wasn't up to temperature.

Could be something dumping too much fuel for the cat to keep up with. How is your gas mileage? Slow 02 sensor or bad coolant temp sensor are two likely culprits for running rich.

Yeah....I'd suspect a lazy sensor, and/or a cat that wasn't heated up.

ciper wrote:How is your gas mileage? Slow 02 sensor or bad coolant temp sensor are two likely culprits for running rich.

Pure short city driving is ~17 mpg and pure highway is ~23 mpg. Just moved from 4300ft to sea level, that might change my estimates a bit. Will know it a few weeks.

As for the cat not being up to temp -- during my 2008 test, I drove ~15 min on city streets to the emissions place. Sat in line for ~5 min and then got sniffed. I'd figure by then it would've been up to temp.

I'll check the O2 and coolant sensors later this week. The info in the chilton manual probably valid?

I don't know if you can check the 02 sensor for slow operation. They usually don't fail outright. How many miles are on both of them?

No idea. I haven't replaced them since I've had the car Aug 2006. Although Nick put in a different engine in Dec 2006, which I assume used at least the coolant temp sensor that came on it.

I don't have access to an old laptop to run the B10 scantool either, to check what the sensors are reporting to the ECU.

If I was to go ahead and replace the O2, I think it would make sense to go with the wideband, since I'm planning on performance upgrades this summer. Is the "LM-1 Wideband O2" the wideband everyone talks about on here? ~$350 is damn expensive. Anyone have the coolant temp sensor part # and price offhand?

I'd go for an inexpensive narrowband sensor for now. You should be able to get one for 30-40 new.

I don't have the part number but as I remember the correct coolant temp sensor (there are two) was around 20$ from https://www.1stsubaruparts.com