Well my Miata is an '03 (Shinsen edition) with about 33K that I've had since Feb '07.
Check Engine light came on 2 weeks ago. Decided to buy a code reader (~$45) and read the alert code a few days ago, which came up as P0455. This is "Evaporative Emission System Leak Detected (gross leak/ no flow)." Maybe this could just be the gas cap? which wouldn't be bad at all.
So yesterday I erased the code, turning the light off, then tightened the gas cap really hard until it gave a click. BTW I am not sure if this is normal, but on my car this takes a somewhat ridiculous amount of torque, far beyond any other car I've driven. Not that I'm the strongest guy around, but I'd wager a significant number of people, including women or people with arthritis or other issues, could not do it. This is why I had previously tightened it short of the click, which worked fine for a year. I also noticed, for the first time, the warning on the cap that says not tightening it enough can make the light go on. All this is starting to like a borderline design flaw to me.
Anyway, I put about 18 miles on it, and so far so good, the CE light is still off. But I think I read somewhere that if there is a real problem and you turn the CE light off, it may take several drives for it to come back on.
So I'm hoping it was just the gas cap, but OTOH if it's something bigger than that I definitely want to take care of it. I'm due to do the emissions test soon and autocross season is coming up. If I drive the car like five more times and the light stays off, can I assume everything's OK?
Thanks Eric