First of all, forgive me if this was addressed elsewhere, but I am new to the forum.

I drive a 2002 Cavalier that has developed a sort of growling noise when the vehicle is idling. It's not something that happens all the time; usually when it's cold outside or I haven't driven the vehicle for very long. I've been told it COULD be either the timing chain or the alternator, but it doesn't sound like the sound is coming from the alternator and I haven't noticed much of a difference in the way the engine runs; it just has that noise.

I HAVE noticed the alternator making a whirring/grinding noise when the car is started (a noise which eventually goes away), but that, to me, doesn't seem to explain the other noise.

The other things I noticed:
-It's losing a slight bit of coolant, but there's nothing on the ground.
-My fuel economy is about 2-3 MPG less (could be the cold weather?)