I just changed my spark plugs, so I had the car out for a test drive to make sure everything was running correctly. I had the radio off, so that I could listen for any problems. We'll when I was sitting at a light waiting to make a turn I noticed a really strange clicking noise. When I got home I parked the car and just sat there and listened to the sound, trying to figure out how often it was happening and where it was coming from. I counted that the sound occurs approximately every 3 seconds, very consistent like a clock. In fact the clicking noise sounds exactly like an analog clock ticking. It sounds as if there is a bomb in my dash or something. As far as I can tell the sound is coming from directly behind the radio area. I took out the CD to make sure that wasnt it, but the noise continued. The strange part is if I turn the engine off, but put the key to On, the noise disappears...Although the sound truly does not seem to be coming from the engine compartment. Any idea what this could be?