You shouldn't be passing the cart in through the url. The cart is an object and can't be passed that way.
I think it should just be:
$eCart1
like:
<?php
$id = $_GET['id'];
function DeleteByID($cart,$id) {
for ($n=0; $n<sizeof($cart->Items); $n++) {
if ($cart->Items[$n]) {
if ($cart->Items[$n]->ID == $id) {
$cart->Items[$index] = null;
$cart->ReIndexContent();
$cart->ResetAll();
$cart->SaveCart();
}
}
}
}
DeleteByID($eCart1,$id)
?>