My car failed smog (JDM B18C), so I'm triyng to figure out what's wrong. I've taken it a million places and ive read so many books, and ive expended all my tests - the only two things (which are pretty big) in doubt are the o2 sensor's readings and the cat.

I am about to replace my cat, which may be the problem, but I'm just wondering if anyone has ever taken an oscilloscope and tested the o2 sensor signal.

mine gets into closed loop and oscillates from the right values, but i have found that at 2500 rpm (not only here, but in other places as well), the cycle takes 1 second or 1.25 seconds to complete (rich->lean reading). Also, it seems that the reading hangs out around the rich side for a hair longer in most cases (not all).

Does anyone know what my wave is supposed to look like at 2500 rpm - or does anyone know some values for the wave that will work at a given rpm that i can compare my values to?

i'm trying to find out if im running rich - i looked at plugs, it seems that there's a fair amount of black carbon buildup not on the tip but on the flat, wide part that the tip is mounted in. Does that mean anything or is that normal?

thanks for the help.

 

bump for any help!

 

bump =[