Since the car has been there so long, I see that people have built that fence over the terrain as it is now.
When you , or some other ‘‘archaeological’’ sucker, extract the rest of the CARcass…
BE READY for that hill back there to settle down into the void you just created over time. AND be prepared for that same hill, with its mud slide history, to end up in your kitchen with the next gullywasher. It is unstable ground, that old car could actually be your saving grace.
Either finish digging to the point of building a retaining wall for the hill ( is that why you’re digging there already ? )…
or fill in the hole with junk dirt.( just as unstable as the hill there that was a landslide 16 years ago )…
or just leave the car there to support the impending land slide.
You’re poking a stick in a hornet’s nest.