knocking sound while idling
 

ok, so I am looking to see if anyone else has experienced this with their Altima.

I have a 2005 3.5 SE with about 23,000 on it. I have noticed recently that when I have been out and about driving around from place to place, when I get back in the car, and start the engine, say, in a parking lot, if its quiet, I can hear this faint knocking sound. I can't tell what it is, but it is getting louder. It doesnt change as you are driving, and it doesnt get louder or softer at all, but it is definitely noticeable. It seems to mostly happen when the engine is hot. It also seems like I can feel a vibration in the gas pedal along with the sound. Anyone have any ideas, or have experienced this yourself? Let me know... [align=right][/align]