ok so today i noticed a new noise coming from my engine. It starts up no problem but going to idles it jumps back and forth a little then wen it settles at 1000rpm it makes a piston slapping noise. It doesnt matter if it is cold or hot it does it not matter what. Engine runs well and have no loss in power. Any reason to worry?

its a 3.4l dohc with a 118xxx miles

would of posted a vid but camera lost. also the noise is quiet i only can hear it in idle