California Smog Fail

[5pointadam]

My 318is just failed smog. Passed at 25mph but failed at 15mph. Has performance chip (not sure of maker). Anyone have experience with failing with chip and passing when you switch back to stock or do I just have to plan on a new cat? Thanks!

Here's my #'s
15mph HC/PPM MAX 124 Measured 232 CO% MAX .78 Measured .55 NO (PPM) MAX 815 Measured 1851
25mph HC/PPM MAX 98 Measured 98 CO% MAX .66 Measured .19 NO MAX 754 Measured 709

[Bimmer0761]

if you do a new cat, make SURE to save your old one i can pay $100 or more as scrap for it if it’s still full inside (or based on how full it is)

[E30_fiend]

I'm recommending you replace your cat and do a tune up. The high HC numbers tell me your cat isn't working at the efficiency that it should and the high NO tells me its running lean and the O2 is truong to switch to an adaptive rich limit in order to protect the motor. Make sure your O2 sensor is working correctly. If you don't know the last time it was replaced, its probably time to do it. They have 100k mile service lives so its not a bad buy. I also recommended the tune up. But at the very least, change your spark plugs. To be honest, I use my smog check time to change my spark plugs. It's a good interval to keep in mind and because the spark plugs are only $20-25, its a cheap way to make your motor run a bit better.

So here's a list of TO DOs:

First and foremost, get a new cat. Yes its expensive but it won't need to be replaced for a very long time. That will bring down your HC numbers dramatically.

Check your O2 sensor or even change it. Won't hurt to change it.

Do a full tune up(cap, rotor and spark plugs) or at the very least, change your spark plugs. Bosch Copper Plus spark plugs only.


Taylor

[CB-M3]

i replaced my original O2 sensor and fixed the vac leaks. it lowered my CO2 and CO ppm significantly. I did not pass the NOx levels so I had to get new cat.