I've read quite a few posts about the Check Engine light, but I'll put this question out there anyway. I just bought a used 98 S70. About a week after buying it, I refueled with the engine still running (yes, I read later that that can cause the CE lamp to turn on, but up here in NH it was COLD). Anyway, I filled up, and drove to work. Later that day I headed home, making a few stops along the way. Later that evening I went out again, and then the CE lamp went on (had driven about a 100 miles since refueling). If refueling with the engine running can cause the CE lamp to come on, I would of expected it to happen immediately. Is it likely that refueling with the engine running did cause the problem (but then why did it take a while for it to come on?) or is it likely something else?

I also read that after driving a while (starting / stopping the engine) the light will reset itself if the problem no longer exists. Any ideas on how many start / stop cycles it takes to clear the lamp?

thanks