I have the exact same problem!!! It has gone away for some time now, and I can't pinpoint it for why though. Hot or cold engine, moist or sunny out, cold or hot out. no idea what is going on but based on my car experience I believe it is a sensor that is malfunctioning for the idle air control if I had to bet. It is throwing the whole thing off but it is wierd cuz nothing in particular I do makes it go away.
I just haven't had time to make it to dealer yet, but my email is
[email protected] and I will contact you when I find something out.
Sucks to by a 30+K vehicle and have this happen.