My 2000 3.0 has developed a chatter from the rh side of the engine compartment. It only makes the noise under a load and I can't duplicate it when the car is on jackstands. I'm thinking it might be spark knock but I can't seem to fix the underlying issue of the emmissions problem i'm having. The car still runs fine but the chatter seems to be getting louder... any help would be great. thanks

 

What underlying isues do you have? It is possible they are connected.