car is making noise which was slow in begning,now has increased & not aceleratin on 2002 Jaguar S-Type

car has a voice from engine its not crank shaft its behind the engine it gets start and make noise as it starts no vibration just voice and it was running with the voice now car is not going up from 3 rpm.. car engine has smoth voice and this voice is different there is no black burning in silencer the blow is perfect please guide me what it could be? 1nce again voice is comeing behind the engine and after 2minuts smoke also come from that area?

Asked by for the 2002 Jaguar S-Type