I have a 1997 Honda Accord LX sedan. It does have high miles, over 120,000 now. I do maintain it very well, and the timing belt and water pump were just changed.
For the past couple of months the car has occasionally been making this rattling sound (it started before the timing belt and water pump were changed). The noise is coming from the front of the car. It sounds like metal vibrating together. It doesn?t do it all of the time, and some days it does it more than others. When I push down on the gas pedal the noise stops.
Any ideas on what?s going on?
usually this is a steel cage or guard around the catalytic converter in the exhaust system.
after a while they can rust out a little bit and get loose. sometimes small rocks get thrown up into them and the pebbles make a heck of a racket too.
you could start the car, and with it running, lay down on the ground beside it and lean a broom handle on the converter guard, see if that stops the noise.
if that DOES stop the noise, you could get a steel hose clamp and put it around the cage to hold it together more to reduce the rattle.
i have heard of some people who remove the guard but that is not a good idea, since the guard protects against catching the grass on fire if you park in high grass. (the catalytic converter gets really, really hot in use)
This was a common problem w/ hondas. The welds for the heat shields around the catalytic converters will break and rattle. Our fix was to simply remove them.
This was a common problem w/ hondas.
And all other makes, including current models as they age. 
Thanks everyone for your help!