Here's the scenario -

When I leave work in the afternoon, I drive out of the lot, and it's 1/2 mile before the first stoplight. Everyday for the past month, without fail, when I reach that stoplight, the engine drops revs to maybe 200, rebounds to normal, and continues this cycle every 5-10 seconds until I get going again. Of course, it's not noticeable anytime other than this first stoplight or at idle. Oddly, in the morning when I head out, I have about 1 mile drive to the first light, and I haven't noticed it doing it at this time. Maybe something about higher ambient temp and cold engine temp, I dunno. Either way, the dealer said they could not duplicate the problem. Ideas?