If coroners become aware of people who have a significant interest in an inquiry, by law they must allow that person time to prepare for and attend the hearing.
"Clearly, it is not possible to give sufficient notice and obtain the evidence required in time for the inquest, which is set down for tomorrow," Coroner Greig said.
The inquest was postponed to early next year.
The Manurewa teenager was killed in December 2010 when he drove a stolen car into a South Auckland fence.
Four passengers, some injured, ran from the scene following the crash, but were later found by police.
Witnesses said the car, which caused damage along a 100m stretch, was travelling about 100km/h when it crashed.
Child, Youth and Family general manager operations Marama Wiki said Isaiah had been in CYF custody since April 2009 and had "absconded" from a caregiver's Kaitaia home on September 20.
An extended family member told CYF the young man was being hidden by his family for at least some of the time he was missing.