The Dodge Dart's sales haven't met expectations since last July's launch.

What started with strong momentum has sputtered badly in recent months and Chrysler officials, all the way up to CEO Sergio Marchionne are desperately searching for a way to kick-start demand for the much-ballyhooed Dodge Dart sedan.

In its first few months on the market, the compact 4-door shot out of the starting gates, with demand particularly strong for its most fuel-efficient versions. But in recent months, Dart demand has dropped sharply.

That’s led the maker to cut output at the Dundee, Michigan plant providing the engines for Dart. But Dodge is betting it can perk things up when it adds another engine option designed to give the sedan more pep, along with a planned 9-speed automatic transmission.

The sedan is performing “not as well as I wanted” since its introduction last July, acknowledged CEO Marchionne during an interview.

On the positive side, sales climbed to their highest level since the Dart was launched, 6,105 in December.  Total sales last year, however, totaled just 25,303.  Of course, it takes some time to build up awareness of, never mind demand for, a new nameplate.  But even with a healthy marketing campaign the new Dodge is running at well under half the sales rate of key competitors such as the Toyota Corolla and Honda Civic, never mind the Hyundai Elantra and Ford Focus.

Industry analysts suggest there are a variety of challenges that the Detroit maker is running up against.  The fact that Dart faces such serious competition is, of course, a major one. And Dodge hasn’t exactly had anything else that offered a serious challenge in the compact segment in quite some years.

But to Marchionne, the biggest problem is that “the powertrains (Dodge used in the Dart are) not the ideal solution.”

As part of its deal with the U.S. government that let it effectively take over Chrysler after the Detroit maker’s 2009 bankruptcy, Fiat promised to introduce a new model getting at least 40 miles per gallon on the highway. And considering the general trend in American fuel prices, it seemed a safe bet that focusing on high-efficiency engines would appeal to the core of the compact market.

On top of that, Dodge bet it would seem a real bargain by offering Dart with significantly more features than many of its key competitors.

But while studies repeatedly show fuel economy tops most American auto buyers’ shopping lists, that doesn’t mean a willingness to accept a serious lack of performance. Dart currently offers two engines and its most efficient powertrain, a 1.4-liter turbocharged I-4, yields as much as 41 mpg with a manual transmission.  But from a performance perspective it’s a classic stone pony.  And the 2.0-liter Tiger Shark alternative isn’t much better.

Sluggish demand for the smaller powerplant has led the maker to eliminate a shift at the Dundee engine plant. Fourteen workers still in their probationary period have been let go, but another 44 are being reassigned as Chrysler prepares to balance out what Marchionne calls “the powertrain grid.”

That means the addition of a new 2.4-liter engine that should boost Dart’s performance significantly without having a major negative impact on mileage.

“It will do well,” Marchionne promised, admitting the sedan “Could have done a lot better if we had done a better job and had all the powertrain solutions in place” up front.

Another improvement is in the works, Chrysler getting ready to roll out an all-new 9-speed automatic.  It will first be used in the replacement for the Jeep Liberty due out for the 2014 model-year, with the Chrysler 200 update to get the transmission next.  That means it likely won’t be introduced on the Dart until the 2015 model-year.