BMW of North America is recalling 156,137 vehicles because they are at risk of stalling or losing engine power, the National Highway Traffic Safety Administration reports.

In these cars, the bolts that secure the housing for the variable camshaft timing adjustment (VANOS) unit might loosen over time and possibly break, NHTSA said. This condition could lead to a reduction in engine power or stalling, posing a safety risk.

BMW dealers will replace the four VANOS housing bolts for both VANOS units -- intake and exhaust. There will be no charge for this service.

The recall is expected to begin in May.

In addition, owners of approximately 170,172 model year 2010-2012 BMW vehicles equipped with inline 6-cylinder engines will receive an extended warranty to address this condition.

The recall covers these vehicles for 2010-2011 model years:

• 128i Coupe

• 128i Convertible

• 328i Sedan

• 328i xDrive Sedan

• 328i Coupe

• 328i Convertible

• 328i Sports Wagon

• Z4 sDrive 30i.

The recall covers these vehicles for 2011-2012 model years:

• 135i Coupe

• 135i Convertible

• 335i Sedan

• X5 xDrive 35i

• X6 xDrive 35i.

 The recall covers these vehicles for the 2011 model year alone:

• 335i xDrive Sedan

• 335i Coupe

• 335i Convertible

• 528i Sedan

• 535i Sedan

• 535i xDrive Sedan

• X3 xDrive 28i

• X3 xDrive 35i.

Also covered are 2010-MY X3 xDrive 30i and X5 xDrive 30i vehicles, 2012-MY 640i Coupe and 640i Convertible vehicles, and 2010-2012-MY 535i Gran Turismo vehicles.

Vehicle owners can reach BMW at 1-800-525-7417.