If I start the car when the car is already warm, there is a rattle for the first 30 seconds and then you will never hear it again. That is until you start it again with the engine warm. The car does not rattle if the engine is cold when it is started, and it doesn't rattle when I am driving. Only the first 30 seconds on a warm start. It sounds like it is coming from the resonator, but I am bringing the vehicle to get checked out soon.