Car has been running fine overall but I've had the CEL come on a few times in over the summer. Twice I had an 0442 (Evap System Small Leak Detected Fault). I've seen this code on my wife's Toyota and it can be something as simple as the gas cap o-ring or bigger like the emission purge valve. I did a forum search here and found similar answers. I've been busy so I just reset it and it doesn't seem to come on after the computer cycles through, it was like 8 weeks later and about 800 miles of residential and highway miles.

Then last week my CEL came on again, I figured it was the same code and was going to check it this past weekend when I had some spare time. Funny thing happened... The CEL went off on it's own. I've never had that happen before but I put the code reader on and it said I did have a code registered, an 0139 (O2 sensor circuit slow response, bank one, sensor 2). So I cleared the code and sure enough it came back on today!

As far as my engine maintenance goes my plugs and wires were new about 30,000 miles ago. Bosch plugs and Magnicor blue wires like everyone suggests. Also I routinely change the air filter, about 2 times a year if driving is normal and more often if on dusty roads. Oh and I did all of my O2 sensors about when I did the plugs and wires. I think I got the ones from AB, the ones that are about $69 each... not the OEM ones that are like $229 each! And I do only run high octane premium stuff mostly from Shell or Valero.

Leaning towards replacing the front bank if the 0139 persists and then if the 0442 comes back I might do a gas cap and the purge valve. From some of the forum posts I read folks have had good luck with the Hyundai 28910-22040 one from Amazon. Any suggestions are welcome.