autocomplete com cake e jqueryUI

autocomple.txt

function admin_busca(){
		$this->layout = "ajax";
		$list = $this->Car->find('list',array('fields' => array('Car.id', 'Car.type')));
		foreach($list as $key => $value){
        $array[] = array("label" => $value, "value" => $value, "id" => $key);
		}
		echo json_encode($array);
	}
========================================
<div class="ui-widget">
		<?php echo $this->Form->input('teste', array('id'=>'teste'));?>
</div>
========================================
var cache = {},
			lastXhr;
		$("#teste").autocomplete({
			minLength: 2,
			source: function(request, response) {
				var term = request.term;
				if ( term in cache ) {
					response(cache[ term ]);
					return;
				}

				lastXhr = $.getJSON("busca", request, function(data, status, xhr) {
					cache[term] = data;
					if (xhr === lastXhr) {
						response(data);
					}
				});
			},
			select: function(event, ui) {
				alert(ui.item.id);
			}
		});