Five episodes into only its fourth season, the CBS sitcom “How I Met Your Mother” seems to be running on fumes.

The show was conventional in its basic premise: hopeless romantic Ted Mosby (Josh Radnor) looks for love in the big city while hanging out with his best friends in their huge apartments and never going to work.

But the talented writing staff (headed by Letterman alums Carter Bays and Craig Thomas) made a modest name for itself by turning the genre’s conventions on its head.

The story is told almost entirely in flashback, as the elder Ted narrates his life story to his children. This allows the show to play around with the narrative by shifting time and making Ted an unreliable narra homage tor.

The writers pay loving to the sitcoms they were raised on while also poking fun at some of their more ridiculous aspects.

But in its fourth season, the show seems to be incorporating more of those timeworn sitcom clichés rather than making fun of them.

In the second episode, the gang travels all over New York City searching for the best burger in town. Why? Well because that’s what wacky sitcom characters are supposed to spend an episode doing. Naturally, there was also a completely superfluous guest appearance by Regis Philbin.

In another episode, the gang starts staging interventions for every small character tic – Ted’s over-pronunciation, for example – including the inevitable “we’re having too many interventions” intervention.

And, of course, Robin’s (Cobie Smulders) news anchor job in Japan would have to involve a monkey throwing marshmallows at her (because Japanese people are really crazy, apparently).

But perhaps the most egregious error was making the show’s funniest character, Barney (Neil Patrick Harris), pine for Robin. The comedic genius of Barney was his unapologetic moral depravity. He manipulated women into bed through daring and creative ways; if he existed in real life, he would be seen as pathetic, but he is so ably played by Harris that he can’t be seen as anything but lovable.

But the writers effectively sterilized him for seemingly no other reason than the “all sitcom characters must fall in love with one of their friends” bylaw in the screenwriters’ handbook. It all just seems so tired and overdone; we’ve seen these things in countless shows before, and they weren’t that funny the first time.

Like many shows, “How I Met Your Mother” was affected by last season’s writers’ strike, forcing several rushed developments. The show attempted to shoehorn in Sarah Chalke of “Scrubs” as potential mother candidate Stella. Chalke did the best she could with the material, but she never really clicked with Radnor, as the writers failed to make her character engaging.

Much of the season was spent on Ted and Stella’s relationship troubles. Every episode featured an angst-filled argument, whether it was about moving to New Jersey, liking “Star Wars” or even whether the two knew each other well enough to get married. It’s never a good sign when a comedy devotes itself more to relationship drama than bringing the funny.

Here’s to hoping the creative staff can right the ship and make “How I Met Your Mother” something more than just another sitcom.