This already exists, downvoted and closed questions will usually be removed automatically.

The exact criteria are listed in this post on Meta Stack Exchange:

Just to formally document the exact policies we have in place to remove old abandoned / dead questions, the Community user will delete questions in the following circumstances:

If the question is more than 30 days old, and ...

• has −1 or lower score
• has no answers
• is not locked

...or...

• it was closed and migrated to a different site

... it will be automatically deleted. Internally, these are termed "dead" questions (RemoveDeadQuestions, or RemoveMigrationStubs in the case of a migration).

If the question is more than 365 days old, and ...

• has a score of 0, or a score of 1 in case of deleted owner
• has no answers
• is not locked
• has view count <= the age of the question in days times 1.5
• has 1 or 0 comments

... it will be automatically deleted. These are "abandoned" questions (RemoveAbandonedQuestions).

These checks are run every week across all sites.

If the question was closed more than 9 days ago, and ...

• not closed as a duplicate
• has a score of 0 or less
• is not locked
• has no answers with a score > 0
• has no accepted answer
• has no pending reopen votes
• has not been edited in the past 9 days

... it will be automatically deleted. These are "abandoned closed", and show as RemoveAbandonedClosed:

This check is run every day across all sites.

See also: The official "How does deleting work? What can cause a post to be deleted, and what does that actually mean?" FAQ meta post.

This already exists, downvoted and closed questions will usually be removed automatically.

The exact criteria are listed in this post on Meta Stack Exchange:

Just to formally document the exact policies we have in place to remove old abandoned / dead questions, the Community user will delete questions in the following circumstances:

If the question is more than 30 days old, and ...

• has −1 or lower score
• has no answers
• is not locked

...or...

• it was closed and migrated to a different site

... it will be automatically deleted. Internally, these are termed "dead" questions (RemoveDeadQuestions, or RemoveMigrationStubs in the case of a migration).

If the question is more than 365 days old, and ...

• has a score of 0, or a score of 1 in case of deleted owner
• has no answers
• is not locked
• has view count <= the age of the question in days times 1.5
• has 1 or 0 comments

... it will be automatically deleted. These are "abandoned" questions (RemoveAbandonedQuestions).

These checks are run every week across all sites.

If the question was closed more than 9 days ago, and ...

• not closed as a duplicate
• has a score of 0 or less
• is not locked
• has no answers with a score > 0
• has no accepted answer
• has no pending reopen votes
• has not been edited in the past 9 days

... it will be automatically deleted. These are "abandoned closed", and show as RemoveAbandonedClosed:

This check is run every day across all sites.

See also: The official "How does deleting work? What can cause a post to be deleted, and what does that actually mean?" FAQ meta post.