In Maricopa county they test diesels every year. The reading is for particulate. They don't test the other readings fortunately. When I bought the car a year ago I drove straight to the testing station and it went thru with 3.1 ppm particulate reading out of 20ppm which is the cut off. This reading was staggeringly low.

I did a long high speed freeway run for about 10 minutes before I went to the station. I do this with all my cars before emissions. Got up to 75 at one stage which is something I never do with this car. I pulled in to the station and there were only a few cars in front of me. So I only waited about 5 minutes. The guy couldn't find the parking brake release! so the first time he was fighting that and it was blowing quite a bit of smoke out before he stalled it!

Then the machine shut down and they had to wait while it re-calibrated. Then the second time there was quite a bit of smoke at the beginning of the test but it cleaned out as the revs increased. They run the plume thru a device that shines a beam to a reflector which I guess is how the particulate is measured.

They also check for any emissions device tampering and the gas cap but as my car has no catalyst and I keep it all original it was all good.

- Peter.

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2021 Chevrolet Spark
Formerly...
2000 GMC Sonoma
1981 240D 4spd stick. 347000 miles. Deceased Feb 14 2021
2002 Kia Rio. Worst crap on four wheels
1981 240D 4spd stick. 389000 miles.
1984 123 200
1979 116 280S
1972 Cadillac Sedan DeVille
1971 108 280S