Can lumbar scoliosis cause fail to maintain erection and/or loss of morning wood? i am talking about mild case noticable only from someone educated.

Not usually: Unless the scoliosis is severe, or is accompanied by disc/spur issues pressing on a nerve, it would be unlikely that scoliosis by itself would cause this. Certainly, it should be looked into, as there are a myriad of diagnoses that can result in impotency. I would recommend initially seeing your family doctor to begin a workup for this problem.