On my NA, the idle was set to 750 by the FSM. About 3 or four weeks ago, I've been noticing that the idle speed seems to drop more and more usually at night with the lights on and brake pedal depressed. I keep watching for an idle lope, but there is none. It's currently running at 750 daytime, and at night, with lights and brakes it goes to about 600-650. Does this sound right, or am I just becoming paranoid? Anyone else have a similar problem or possible solution, or even probable cause?

 

Sounds like what mine was doing. I believe its a combination of the wirring of the car and the alternator.