You can use the wordpress save_post
action to update the title
using the custom fields as you like. Here is the simple example I have used myself –
add_action( 'save_post', 'custom_post_type_title' );
function custom_post_type_title ( $post_id ) {
global $wpdb;
if ( get_post_type( $post_id ) == 'job-updates') {
$terms = get_field('job', $post_id);
// taxonomy fields return an array, use the first term
$term = $terms[0];
// get date field
$date = get_field('date', $post_id);
// set post title/slug
$title = $term->name.' '.$date;
$where = array( 'ID' => $post_id );
$wpdb->update( $wpdb->posts, array( 'post_title' => $title ), $where );
}
}