Search trough all WordPress pages and ALL the custom meta values.

gistfile1.php

<?php

global $wpdb;

$keyword = get_search_query();
$keyword = '%' . like_escape( $keyword ) . '%';

// Search in all custom fields
$post_ids_meta = $wpdb->get_col( $wpdb->prepare( "
    SELECT DISTINCT post_id FROM {$wpdb->postmeta}
    WHERE meta_value LIKE '%s'
", $keyword ) );

// Search in post_title and post_content
$post_ids_post = $wpdb->get_col( $wpdb->prepare( "
    SELECT DISTINCT ID FROM {$wpdb->posts}
    WHERE post_title LIKE '%s'
    OR post_content LIKE '%s'
", $keyword, $keyword ) );

$post_ids = array_merge( $post_ids_meta, $post_ids_post );

// Query arguments
$args = array(
    'post_type'   => 'page',
    'post_status' => 'publish',
    'post__in'    => $post_ids,
    'posts_per_page' => 20
);

$search_query = new WP_Query( $args );

?>