Luckily, this is not one of the worst Porsche engine issues.
Porsche has a rocky history when it comes to recalls. The company doesn't issue recalls very often, but when it does, the issues can be catastrophic. Take the 991.1 GT3 for example. That car had the issue of catching fire, so Porsche needed to recall them and give the owners new engines. There was also the 996 911, which had the infamous IMS issue where the engine basically grenaded itself. Porsche just issued a new recall in the US for 18,000 Cayenne and Panamera models, but luckily the issue is not as severe as those other cases.
The issue specifically lies with the camshaft controllers within the engine. These controllers may come loose inside the engine, causing it to stall. This increases the risk of a crash. To fix the issue, Porsche will replace the fastening screws for the camshaft adjusters free of charge. The recall affects 18,000 2010-12 model-year Porsche Panamera S, Panamera 4S and Panamera Turbo models, 2011-12 model-year Panamera and Panamera 4 models, and 2011 model-year Cayenne S and Cayenne Turbo SUVs. The company has not issued an owner-notification schedule, so owners are encouraged to call Porsche or the NHTSA.
Porsche can be reached at 800-767-7243 and the National Highway Traffic Safety Administration's vehicle-safety hotline can be reached at 888-327-4236. It is good that Porsche is out ahead on this issue even if the problem only affects a small number of cars.