This problem seems to show up maybe once a month. Last night I'm sitting at a redlight and all the sudden the idle gets real rough and dips to around 500rpm. It then drops to 0 for a split second and bounces back up to 500, but didn't die. I can turn the car off and restart it, and it will idle fine for another month or two.

 

Sounds like an Idle control valve on the beginning of death or possibly a low coolant condition .You can check the coolant level (make sure the car is cold) if it is good have the dealer look over the idle circuit in your car .

Jens

 

Mine does that too....but it doesn't go all of the way down to 500 Its just a light shudder.