Volkswagen diesels may be practical and fuel efficient, but perhaps not flawless.

The National Highway Traffic Safety Administration (NHTSA) has launched an investigation into stalling problems with 2009 Volkswagen Jetta TDI diesel cars. According to the investigation, there have been seven complaints that the cars have unexpectedly stumbled, then almost immediately stalled while driving. NHTSA is looking for more information on how frequently this occurs and its potential safety effects. If you own a TDI and have experienced the problem, you can add your experience by filing a complaint on NHTSA's website.

We have been impressed with the two current-generation Jetta TDIs we have tested, a 2008 sedan and a 2010 wagon (coming soon), for their impressive fuel economy well-finished interiors and enjoyable driving dynamics. We were also impressed with the Golf TDI hatchback we tested. While we reported on our manual transmission-equipped 2010 Jetta and Golf TDI being overly easy to stall in some low-speed situations, such as second-gear stop-and-go traffic, we haven't experienced stalling as described in the NHTSA report.