Found a feral kitten hiding in the engine of my car!

There was a very thin kitten at my bird enclosures eating the bird food. It ran under the car.
It initially hid on the tyre and then disappeared when I found it. I later coaxed it out making meow sounds. I tried to offer it food and it hid again. My son opened the bonnet and I saw it hiding in the engine. I slowly reached in and held it and managed to pull it out of the engine. It is extremely thin under the fur.
It is eating small amounts of food and is sleeping on my chest. I suspect it hasn't eaten for many days or even over a week as all it' bones are sticking out. It has warmed to me quickly, possibly because it is so desperate for company and food.
I expect it is 6 -8 weeks old. Possibly older but looking smaller from starvation.
PS it’s a girl.