Hi thanks for the reply. After a series of checkups and consultaion, just yesterday it has finally been spotted. The culprit was the belt tensioner. The screw holding the roller is totally damaged and lost its thread. Maybe a little longer it could have flown away from the assembly. Thank God! The vibration is gone but few more problems were spotted again like the axle boots and lower arm bushing, and 1 of the engine mounts needs replacement. Kinda disappointed cause my Mazda 3 before did not give me any problems like these until the time I sold it at 117K. Don't misunderstand me, I'm also a nissan fan. Thanks so much for your suggestion Mr. Mayur. I believe your suggestion would be one thing to look at in the future. And I hope my case would help other owners pin point theirs too if ever this occurs. Have a nice day and Happy New Year!!