Been reading up on the idle issues because I am experiencing the same thing off and on - rough idle in Drive when at temperature while at a light. So, I will go ahead and clean my IAC this weekend.

However, what I noticed today by messing around, is that when I turn on my rear defroster, I'll get that nasty vibration. I also hear a click over at the fuse panel. When I turn on the AC, it is not as bad.

Any thoughts, ideas?

Thanks,

Chris

My idle drops in my car (2002 Corolla) when I turn on the rear defroster. There's a click because it sets off a relay that sends current to the rear defrosting panel (quite a bit of current, mind you).

yeah its the relay tripping and drain on the alternator that effects the idle