check engine(catylist efficiency code?)

$52821343&categoryc24&rd=1> > ...I flew down to Texas last week, from St.Louis(USA), and drove back the> > 800 miles to southern Illinois. It was a great trip, except for the fact> > that it rained for about 700 miles! The car ran great. I averaged close to> > 30 mpg! A big chunk of the trip was on the Oklahoma turnpike @ 80mph! When> > I filled up the gas tank in Texas, I mistakenly forgot to get the three> > "clicks" on the gas cap...you guessed it...check engine light came on. When> > I got home, I unhooked the battery for an hour, and the check engine light> > went out. 2 days later, while driving to St.Louis, it came on again. I> > unhooked the battery overnight, and 2 days later, the check engine light> > came on again. I've checked (to the best of my ability) all of the vacuum> > hoses. I've changed all of it's fluids to Mobile1 synthetic. Put in a K&N> > air filter. Other than the check engine light, the only real problem I've> > had was 2 clogged drains for the top...darn those Texas leaves! I had a> > small amount of water in the trunk, and I had to remove the back sill> > material that was pretty wet underneath. I hooked up a shop vac to a> > section of clear tubing (the same tubing that I used refill the transmission> > oil) which fit perfectly into the two clogged drain holes. Many thanks to> > the people on this ng! I've learned a lot over the past week or so. > > seeya...jim> >

It seems self-explanatory to me. The catalytic converter is gone. Here is a link:

Leon

Try it without the K&N filter - put in a Mazda replacement filter and see if it stops. I know it sounds stupid, but my wife's Honda Accord will throw a code on anything but a Honda filter and the dealership (one I actually trust) told me it's not unusual in today's world given all the sensors. Never heard of it on a Miata but can't hurt to check. The next best bet is probably the 02 sensor since it has a lot to do with mixture which in turn has a lot to do with the catalytic converter. Good luck and enjoy the car.

Tom

92 Red

jimuntch wrote:

$52821343&categoryc24&rd=1> ...I flew down to Texas last week, from St.Louis(USA), and drove back the> 800 miles to southern Illinois. It was a great trip, except for the fact> that it rained for about 700 miles! The car ran great. I averaged close to> 30 mpg! A big chunk of the trip was on the Oklahoma turnpike @ 80mph! When> I filled up the gas tank in Texas, I mistakenly forgot to get the three> "clicks" on the gas cap...you guessed it...check engine light came on. When> I got home, I unhooked the battery for an hour, and the check engine light> went out. 2 days later, while driving to St.Louis, it came on again. I> unhooked the battery overnight, and 2 days later, the check engine light> came on again. I've checked (to the best of my ability) all of the vacuum> hoses. I've changed all of it's fluids to Mobile1 synthetic. Put in a K&N> air filter. Other than the check engine light, the only real problem I've> had was 2 clogged drains for the top...darn those Texas leaves! I had a> small amount of water in the trunk, and I had to remove the back sill> material that was pretty wet underneath. I hooked up a shop vac to a> section of clear tubing (the same tubing that I used refill the transmission> oil) which fit perfectly into the two clogged drain holes. Many thanks to> the people on this ng! I've learned a lot over the past week or so. > seeya...jim>

>

Funny you should ask! I had a go around with this a year ago. The original cat was known good, and the cat eff code would not set. It only came on with the older small cat FMII midpipe in place. Set the mid pipe back, and the cat was replaced with a larger one. End of problem.

The light was setting as a result of failing the fed driving cycle tests that are part of OBDII. Seems that the small cat was a two way cat converter, and the stock cat three way. (More efficient.) Next, low speed (city driving) did not heat the small cat up enough to purge it properly. Running it on the highway every three days or so drastically reduced the number of nusance trips for cat efficiency. Its also possible that poor ignition or even sticking injectors can cause such things. The O2 sensor sees an average of all four , and one cyl out of whack can cause mixture problems by fooling the O2 sensor. Finally, the front O2 sensor can cause the problem if it's output is just a bit low.

$52821343&categoryc24&rd=1> > > ...I flew down to Texas last week, from St.Louis(USA), and drove back > the> > > 800 miles to southern Illinois. It was a great trip, except for the > fact> > > that it rained for about 700 miles! The car ran great. I averaged > close to> > > 30 mpg! A big chunk of the trip was on the Oklahoma turnpike @ 80mph! > When> > > I filled up the gas tank in Texas, I mistakenly forgot to get the three> > > "clicks" on the gas cap...you guessed it...check engine light came on. > When> > > I got home, I unhooked the battery for an hour, and the check engine > light> > > went out. 2 days later, while driving to St.Louis, it came on again. I> > > unhooked the battery overnight, and 2 days later, the check engine light> > > came on again. I've checked (to the best of my ability) all of the > vacuum> > > hoses. I've changed all of it's fluids to Mobile1 synthetic. Put in a> K&N