My titan has 69000 miles on it, after driving it distances of 1 hour or more then shutting the engine off for 30 minutes or more & crank it up again it blows out a cloud of whitish gray smoke for about 5 seconds. It does not do this unless you drive it for long distances. Dealership said it was pcv valve but changed them, still same problem. I have no water in the oil, & no oil in the radiator. Has anyone else had these problems?