My check engine light has been going on and off for the past two months since I had my last oil change... it started like the next day. I have a feeling that some of the time it's been the gas cap, as it was going on a lot when I went to one specific Lukoil, which I've stopped going to... but I also noticed it happens a lot when it rains.

At the dealership who did the oil change, they tried telling me I need new air filters. I told them no because I'm about to turn in my lease. So now that I'm turning it in, I want to check what might be causing this problem. Engine runs fine except at low rpms in 6th gear I feel it occasionally stutters more than it should.

Does anyone whose more technical oriented have any hints? I'm thinking they might have accidentally not reconnected a sensor or did something during the oil change that could be causing this - something I could easily check myself.

My dealer says don't worry - that they can get the light to turn off before the "inspector" comes to bill me for any excess wear, but I still want to double check it myself.