Pressure test your cooling system. White smoke is an indicator of coolant, blue is
oil, black is fuel.
If your cooling system will not retain pressure it is indicative of a bad gasket seal (intake manifold ot head gasket, assuming none of your hoses are leaking) and will allow coolant under pressure after shutdown to enter the intake manifold or combustion chamber. Frustrating I know.
Best of luck to you.
Rick