Back in October 2013, General Motors announced plans to launch a "bi-fuel" version of its new Chevrolet Impala full-size sedan.

It billed the planned Impala variant as the only production full-size sedan capable of running on both gasoline and compressed natural gas (CNG).

But more than a year after its public debut, the natural-gas Chevrolet Impala still isn't available to consumers.

DON'T MISS: 2015 Chevrolet Impala To Be Offered As Bi-Fuel Model With Natural-Gas Tank (Oct 2013)

The car was originally supposed to go on sale in summer 2014, but roughly a year later, there's still no confirmed indication of when it will arrive in dealerships.

GM continues to hold deliveries of bi-fuel Impalas pending a fix to an unspecified quality bug, reports Automotive News (subscription required).

In a May 29 memo to Chevy dealers, GM said the Impala will be subject to a "second quality hold" while the company tweaks its CNG fuel system.

2015 Chevrolet Impala Bi-Fuel Natural Gas

2015 Chevrolet Impala Bi-Fuel Natural Gas

The Impala bi-fuel includes complete fuel systems for both gasoline and CNG, with a 7.8-gallon steel tanked mounted in the trunk to store the compressed gas.

The GM memo listed a tentative shipping date of "mid July," but said some dealer orders placed in April and May "will not be produced."

GM wouldn't discuss the problem with Automotive News, but acknowledged that it is working to implement a fix for the 200 Impala bi-fuel sedans that have been built so far.

ALSO SEE: Natural-Gas Powered 2015 Chevy Impala To Start At $38,210 (May 2014)

Those are all considered 2015 models. Dealer ordering and production of 2016 models will reportedly begin in the third quarter of this year.

All cars are built at the same plant in Oshawa, Ontario, that builds most Impala models. They're then shipped to Michigan to be equipped with the natural-gas system by an aftermarket company.

The bi-fuel model shares a 3.6-liter V-6 with other Impala models, although its version has hardened valves and valves seats for better durability when used with CNG.

2015 Chevrolet Impala Bi-Fuel Natural Gas

2015 Chevrolet Impala Bi-Fuel Natural Gas

Chevy says the Impala can travel 150 miles on CNG, while its combined range on gasoline and natural gas is estimated at 500 miles.

A base price of $38,210 (including destination) was announced last year.

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If the bi-fuel Impala does go on sale, its only real competition will be the Honda Civic Natural Gas--along with an assortment of trucks and vans.

At the time, GM said it expected to sell just 1,000 bi-fuel Impalas during the first year.

That goal, of course, will require the car actually to go on sale.


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