The problem started when the really cold weather hit, not sure that matters. The car cranks fine but idles rough after cranking. This last for a few seconds then its fine. When I drive off; however, it hesitates then suddenly surges forward . I had a new battery put in by the dealership and they also replaced the "upper vent valve" and did a "valve assy-purg". The problem was still there so I took it back in. Now they say its "Rod/Bearing with the #6 cylinder" so they need to replace the whole engine. Something about "accessive clearance". Thats a $7500 repair. Does this make any sense?