I typed in Site Search engine, like that, no inverted commas, and got a billion irrelevant threads. Then I typed in "site search engine", like that, in inverted commas, and I got ONE result! Hooray!! Success!!!... but it was about the Starship Enterprise.
Actually, I just found out that if you put whatever you're searching for within quotation marks ("), it narrows it down to what you're looking for. At least it worked for me.
That and several more methods are listed in a pop-up window if you click on the blue "search tips" link, located near the search window. They're typical search methods. The important thing is the engine is (more or less) working instead of giving a "go back to previous page."
I must be doing something wrong. With or without quotation marks I'm still getting 90% irrelevant stuff. I just did a random experiment - a search for topics about Gerald Fried - and although several topics in a long list did include his name, many of the threads had his name as part of the topic content... which might be useful in itself, but it also linked to posts where someone might have mentioned eating "fried" eggs. The majority of posts were still a lucky-bag of anything and everything.
Hmm. Yes, it does appear that the hits reflect the terms both in the title and within threads themselves. No way to narrow it down to just titles, for example. But at least the results are far more specific than before, when using quotation marks.
Be sure, however, to write "gerald fried", not "gerald" "fried".