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Cats don't "light up" or "ignite." They operate most effectively at a specific temp range. What engine temp did you do the test at? If on a cold engine, then that's almost certainly your problem. If on a fully warmed up engine, then it could be the cat, or it could be other problems -- o2 sensors, injectors, ignition components, etc. Anything that was preventing full combustion. What were the numbers, and what engine temp did you do the test at?
It was after a good run but I got stuck in slow traffic as I dropped the car off so it cooled off some. Engine was hot.
didnt get the numbers - it was only just a fail. Hence my assumption the Cat wasnt at the correct temp.
rechecked ignition & no codes.
car Is running the best it ever has.
I was close to failing on Nox once and I asked the tech what would cause this. He said getting the car too hot can cause high Nox readings. I had driven the car for hours before the test so it seemed a possibility.
The next time I was due for a test I just went for a 15 minute freeway run to warm it up and it passed easily and has ever since.
Without the numbers everyone here is just shooting in the dark as to a cause.
That explains the 15mins to pass state. Thanks.
mine has 148k so it did pretty good although the cat on my Subaru has 280k and still passes with flying colors.
Found the numbers:
803 rpm, HC=137 (100 max)
CO2= 15.4%, O2= 0.1%, CO= 0.04%
Interesting you did test at idle. Both mine were at load. Also standard California smog. Are u 4wd? photo329.jpg
I failed 25mph test. Tech told me because I didn't drive enough. Filled gas tank with 1 bottle Swepco 503 and drove until tank was empty. Added 1bottle Techron to another fill up and also drove entire tank. 400miles of spirited "Italian tune up" driving. Put fresh gas retested and passed.
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Lighting up the CAT
