I am in the process of waiting for a new cat converter to be delivered for
my 2000 Protégé (1.6L). It appears to not be working all that well,
according to the test report the other week when it failed CA emissions
testing.

Of course, I am curious as to why it failed. It clearly does not have it's
guts rattling about;  it merely isn't the little furnace it used to be.
Obviously, I would prefer to not have to replace it again soon (or ever)
once this exercise is complete.

So thanks for the input, Alex. I thought about it a little and decided to
pull one of the spark plugs out and see what it might tell me about the
condition of the mixture. This is a new car for me, so anything I do like
this is total discovery. First plug was really loose. It was a Splitfire
(which, frankly, I think is an example of what happens when marketing folks
get a little too close to the real product). Good news was that the color,
shape, etc was a fairly decent representation of a "good" plug. Second plug
was a something or other....but not a Splitfire. Hmmm. Wonder why? It also
appeared to have good burn characteristics and was in there kind of loose.
Third plug, another Splitfire, was probably the most correctly torqued of
the bunch. It also looked good and the final Splitfire required almost zero
torque to get it moving. It also looked OK.

So now there are four, new Densos in there, all happily seated at 15 lb/ft
and lubed with anti-seize from my lifetime supply tube.

I did not do a compression check of the engine, but I am pretty certain,
based on the way it performs, that none of the valves are bad. All in all, I
don't see any evidence that the head is running either rich or lean. Like
the little bear's bed:  it seems just right.

Of course, I still don't know for certain why the converter crapped out. Let
me be careful with that statement:  If the new converter solves the emission
problem, thereby demonstrating that the one I just took out is bad, then I
will not know for certain why the converter failed.

Ken