Search function is not ok

Opencart 1.5.1.3

I don't know what's happen but the search is not ok.
When i'm looking for an product with 2 words (2 tags), the system returns me a lot of products and page of product that has nothing about what I want. When I put just one word to search, then returns the right products.

But I imagine what all the people usually does when they wanna looking for something. I think that they always use more than one tag... I do this way.

Please, does someone know what's happen with the search function?

I tried to change some words in catalog/model/catalog/product.php but wasnt work

Thanks very much

I'm brazilian, so don't worrie about my english

the problem is with their search system in the current 1.5.x opencart. There are a few extensions to improve on it though

What is the url of your website ? Can you give to me an example of two words expression that don't turn proper results ?
I am not using any extension for search function for my website as search is search , you input and get the result.
Check on product form pages (when you log in to admin, product edit, on the first form page are the fields for title, description and meta description) and the lowest row it's "Product tag" field: are there any words written there ?

then take a look at some other well-known ecommerce sites like http://www.ebuyer.com or http://www.dell.co.uk who are even worse.

For example, if I enter the easy to understand search term 'linux desktop computer', eBuyer comes back with a long list of non-relevant items in its first 10 entries, such as USB drives, flash drives, SSD drives, an HP ProLiant Server box etc., yet not a sinlge genuine hit!

Or, if I search for 'Linux PC' on Dell's website, it comes back with a long list of laser printers.