There's a rattle that seems to come from the engine on my 03 Protege ES when I hit the gas. It only happens when I'm gear, at low revs and low gears (1-3). It seems to happen after I've been driving for a while (10 minutes). It's more like a clicking sound. A bit like hitting two marbles together. My first thought was that it might be the clutch since it only happens when in gear. Any thoughts?