You are not an adult under the definition in the State of Michigan until you are 18. If you leave, you can be forced back home because you are still a child. If you want to live with your grandparents and your parents do not agree, then you need to stay with your custodial parent. If you want the Court to step in, you will need to have your grandparents file for guardianship.
Wait it out. You are still a child under the law and it will likely be enforced.
***Answering legal questions is a complex matter and cannot be done without further research. My answer here is based solely on the information given in the question and should be taken as informational only. This is not legal advice. My answer here does not indicate that I represent you now, or that I will represent you at a later time. I take clients on a case-by-case basis, and only after initial consultations. ***
Sign up to receive a 5-part series of useful information and advice about child custody law.