B6 s4 rattle when warm and low rpm
 

I have a b6 s4 that just started to have a rattle at low rpms and ant start up. Only happens when warm and doesn't happen everytime. Any ideas?

Timing chain guide or tensioner may have failed and slacking the chain, meaning engine or transmission needs to come out and timing chains replaced. Google audi 3.2 and 4.2 timing chain failure. If you dont repair it soon it will come apart and destroy the valves, and be huge huge money to repair.