Set config item not working

[eluser]Unknown[/eluser]
TRY this :

$this->config->load('tweet', true);//load config first

//begin set new value
$this->config->set_item('tweet_consumer_key','your new value');
$this->config->set_item('tweet_consumer_secret','your new value');

$this->load->library('tweet');//if you have lib connected to config place here


echo $this->config->item('tweet_consumer_key');


//hope that would help...