Cadillac Repair: 90 DEVILLE, auto parts store, carbon buildup

Question
SOME TIMES WHILE ON THE GAS WHEN DRIVING I HEAR A RATTLING NOISE WHAT COULD THAT BE

Answer
This is normally caused by a carbon buildup on top of the pistons or by using the incorrect octane fuel.

Try using a higher grade of fuel and see if the noise continues, If it does, You will need to purchase and use a product called TOP ENGINE CLEANER available at any auto parts store and follow the directives EXACTLY.

This noise can also be cause by late ignition timing. Has any work been performed on the vehicle prior to this noise ?.