2002 Nissan Altima Rattling sound when pressing on gas

Noises problem
2002 Nissan Altima 6 cyl Wheel Drive Type unknown Automatic 57,000 miles
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Lately when I press on the gas, it makes a rattling sound almost as if something is loose. Have any idea what it may be? Again, there is a rattling noise upon gas acceleration and sometimes even for a few minutes after letting off the gas peddle. Hope you can help me.

Thanks,
Jeanne