I hear an intermittent ringing noise during idle at some start ups. It doesn't occur at all start ups but seems to be more prevalent on the colder starts. My A/C makes a ringing noise when turned on but that isn't the cause in these instances because the A/C is turned off. Any idea(s) what may be making this ringing noise ? BTW, my Maxima has a slow idle. Maybe ~ 500 to 600 RPMs. Is that too slow or typical for the ' 02 Maximas ? Thanks.