I have an '07 Sonata 3.3 that is noisy at cold start-up. If the ambient air temp is less than about 15 degrees, you can hear what almost sounds like piston slap at idle for about 20 seconds. Cold start up with air temps over 20 degrees, there is no noise until you put it in gear and get a load on the engine - then the noise is evident for several seconds and then fades away. Anyone else experience this?

 

The noise is chain tensioners.