My engine seems to have a louder. Sound when running and when I shut off engine it takes a second after key is turned that rumbling stops.Also ther is a noise unde front of car that rattles when going over small bumps or bumpy ashphalt.Maybe shocks, loose brakes, struts?
what maintenanceis service requirements for 80k miles and over or under? on 2005 Nissan Altima
Its hard to speculate without hearing the sounds first hand but I have seen the exhaust heat shield under the car deteriorate and corrode to the point where they cause a rattle. Could also as you say be suspension related or sway bar link end bushing related. I have heard also of of some of those engines having the cat.converters break up and cause engine damage so it may be prudent to get it checked out as soon as you can.