'96 Civic Engine Issues

Hey all, I'm having issues with my honda civic. First of all the check engine light is on but I had that checked out at autozone and the machine said that was a catalytic converter failure, with a number of possibilities causing it including engine problems. Just curious if anyone knew exactly what a catalytic converter failure is going to mean to me.

However, my real problem is this, the engine is making a wholllleeee lot of noise at low rpms and when stopped, it sounds like a fast rattling almost, and when I opened the hood to listened, it sounded more like it was coming from the radiator, but I'm no car expert, but I was wondering if anyone had any experience with lots of engine noise at low rpms, and the noise stops when I hit the gas and the rpms go higher. Alright take care. Thanks!

There's a lot of things that can be and if it's really coming from
the engine it probably is a serious issue. One that could only
be truely verified by tearing it down and looking.
Sounds like maybe a loose rod, but maybe a valve train problem
that could easily be fixed by pulling the valve cover and readjusting
the valves. To many things to try and guess without hearing it.
Get a stethascope and isolate where the sound is coming from.
that'll narrow the possibilities a lot.
Most catalytic converters go out because of a different problem,
like dumping unburned gas in them. They are usually the result
of another problem.
They don't die, they're usually murdered.:smokin: