305 tpi. High miles
Here's the readings.

HC (ppm)
max 110 meas. 160


no (ppm)
max 772 meas. 938

What do you guys think?
I should also say that I did not drive it on the weekend and took it in this morning for smog after driving it a short time. Is it possible I didn't heat the cat up enough?



Thanks for the help

 

Anyone possibly have any answers? I'm wondering if I didn't heat things up enough before I went in. Woudl more heat in the cat bring my 15mph nox down 200 ppm?

 

Drive around for about 1/2 hour before testing. This should get the cat lit up and working. If it still fails, then it could be a bunch of other things, including the cat. The measurements are not way off, so maybe the hot cat may help. To reduce the NOx emission fill the tank with premium, check the ignition timing (excessive spark advance increases NOx), make sure the EGR valve is operating and the passages are free of carbon. A new set of plugs, and a clean air filter should help with the HC.