I could achive this by making the following changes:
File: wp-includes/query.php
REPLACE:
$search .= “{$searchand}(($wpdb->posts.post_title LIKE ‘{$n}{$term}{$n}’) OR ($wpdb->posts.post_content LIKE ‘{$n}{$term}{$n}
WITH:
$search .= “{$searchand}(($wpdb->posts.post_title LIKE ‘{$n}{$term}{$n}’) )”;
REPLACE:
$search .= ” OR ($wpdb->posts.post_title LIKE ‘{$n}{$term}{$n}’) OR ($wpdb->posts.post_content LIKE ‘{$n}{$term}{$n}’)”;
WITH:
$search .= ” OR ($wpdb->posts.post_title LIKE ‘{$n}{$term}{$n}’) “;
