CA Smog Test Question Re: HC - 986 Forum - The Community for Porsche Boxster & Cayman Owners

jim_hoyland · 07-20-2014, 02:13 PM

My past two California Smog tests passed. One of the parameters has me concerned. The maximum HC ( PPM ) allowed at 15 mph is 58 ppm; in both my prious two tests the measured was 57 ppm. At 25 mph, there was a larger cushin, the low speed one has me concerned.
Each test was performed on a hot engine, I use Chevron with Techron, and prior to the last test I added one of those bottles of Techron.

My other parameters are in line and not in danger of failing. Any suggestions will be appreciated. If the other test results are needed I could add them...

SoCalBlackbox · 07-20-2014, 02:32 PM

The last test on my 2000 base 33k miles (3/31/14) showed 1 HC (PPM) at 15 mph and the same at 25. The CO(%) was 0 and the NO (PPM) was 0 the CO2 was 14.7%.

Don't know what year or model yours is. Hope you pass, it's always stressful with older cars.

Rick

Topless · 07-20-2014, 03:36 PM

Year and mileage? My car is borderline HC with 112k miles and I suspect leaky injectors. A spirited 30 minute canyon run prior to test is my plan next time. I did not do that before the last test.

jim_hoyland · 07-20-2014, 06:39 PM

It's a '98 with 60K miles. It has been suggested that o2 sonsor(s) cold be at the heart of the problem.

The most interesting thing I've noticed is the similarity of results after two years.

steved0x · 07-20-2014, 07:35 PM

What if you were to fill up with 87 before the test? Would the computer reduce the power and so you would burn less fuel and therefore less emissions at a given speed? Or is that crazy talk. I was just thinking that as I read this thread...

Topless · 07-20-2014, 09:11 PM

Quote:

Originally Posted by jim_hoyland

It's a '98 with 60K miles. It has been suggested that o2 sonsor(s) cold be at the heart of the problem.

The most interesting thing I've noticed is the similarity of results after two years.

Aging O2 sensors will throw a very specific error code and CEL so they are possible but less likely. Aging cats, MAF, or leaky injectors are more likely. With a Durametric scan you can get a closer look at fuel mixture trims and cat efficiency which might narrow down the problem. If the car is trimmed nearly full lean but still running rich it points to a bad MAF or injectors.