The Lincoln Zephyr sedan hasn't been out four months yet and Ford Motor Co. is already planning a makeover that will include a more powerful engine, a flashier front end and a new name -- the MK Z.

The MK Z will debut Wednesday at the Chicago Auto Show and will reach showrooms later this year as a 2007 model.

The MK Z will be the first sedan on the road to feature Ford's new 3.5-liter V-6 Cyclone engine and six-speed automatic transmission. It's the same powertrain featured on the Ford Edge and Lincoln MK X crossover vehicles that will be launched this fall. The new 250-horsepower engine gives the MK Z another 29 horses under its hood than the Zephyr.

Like its predecessor, the MK Z shares a Mazda6-inspired platform with the Ford Fusion and the Mercury Milan. Critics of the Zephyr said it offered too little to differentiate itself from its siblings.

"They understand that there's some shortcomings," said Erich Merkle, an analyst with IRN Inc. in Grand Rapids. "It says they're addressing them."

But Peter Horbury, Ford's executive director of design for North America, said the redesign of MK Z is not an admission that the Zephyr isn't up to snuff.

"We just gave a new face to the new powertrain," he said Monday. "We're trying to make Lincoln slightly different from the others."

The Fusion and the Milan will not get the new engine for the 2007 model year. However, like the MK Z, they will add all-wheel drive as an option.

"This was planned from the start," said analyst Jim Hall with AutoPacific in Southfield, adding that Ford rushed the Zephyr to market in order to fill the gap created by the demise of the Lincoln LS sedan, which the company plans to stop producing in April.

That strategy required Lincoln designers to limit their changes to the underlying Fusion design. Since front-end modifications are among the most complicated from a production standpoint, this was one area that had to wait.

"The front was the weakest part of the Zephyr," Hall said. "(But) it was what they had to do to get it done fast … They needed product for the dealers."

Lincoln sold 19,109 LS sedans in 2005, down 29.4 percent from the previous year. Since its launch last fall, the Zephyr has sold more than 7,600 units. In January, Lincoln only sold 873 LS sedans, compared with 2,692 Zephyrs.

The MK Z is more reflective of the new Lincoln design theme, a look exemplified by the new Lincoln MK S flagship sedan that was unveiled at the North American International Auto Show in Detroit last month.

It also offers a new metallic interior option in addition to the existing wood trim options offered in the Zephyr.

As for the name change, it reflects Lincoln's new alphabetic naming scheme -- a type of nomenclature often used by European automakers to emphasize the brand over individual models.

"We felt that we still had time to make the change," said Ford spokeswoman Sara Tatchio, noting that the Zephyr name was still too new to have built a strong resonance with consumers. Analysts agreed that the name change would cost Lincoln little in the marketplace.

However, Merkle said it would take more than a name change, a design refresh and new powertrain to make the MK Z a real challenger to the likes of the Cadillac CTS and BMW 325i, which are in the same price range.

"It certainly is a move in the right direction," Merkle said. "(But) I still don't see it as a real competitor with other vehicles in the entry-level luxury segment."

The Fusion and the Milan will not get the new engine for the 2007 model year. However, like the MK Z, they will add all-wheel drive as an option.

"They understand that there's some shortcomings," said Erich Merkle, an analyst with IRN Inc. in Grand Rapids. "It says they're addressing them."