How to trigger change detection when array object is modified?

In my angular4 app i have a component with a *ngFor directive based in a array:

 <div *ngFor="let person of persons">
   {{person.name}}
   {{person.car}}
 </div>

In the other part of the component im able to delete a car, so in the subscribe of the deleteCar() method i update the persons array to:

 deleteCar(car) {
   this.carService.deleteCar(car).subscribe(() =>  {
   this.persons.filter(obj => obj.car == car.name)
               .forEach(i => i.car = null);
   }
 }

The problem is that the *ngFor loop is not triggered when i modify a existing person object in the persons array. How to solve this?