2006 Accord. Indicator Lamp came on about a week ago and is not relatedd to a loose gas cap. Owner manual says it means I have a problem with the emission system. Only symptom I have noticed is that it idles a little rougher than usual, and it will occasionally stall when at idle. Reminds me of a problem I had with an old Civic--then it was usually that a fuel filter needed replacing. This engine isn't as easy to work on, and I don't even know if that is a possibility, or if that type of repair is over my head. Any ideas? Are there any additives worth trying?

Thanks