There have been rumors for weeks that the Chrysler Pacifica might have a stalling issue. Now a consumer advocacy group is asking NHTSA to investigate the alleged problem with an eye to recalling 150,00 of them for a potential safety risk.

On Monday, the Centre for Auto Safety formally asked the National Highway Traffic Safety Administration to investigate Pacifica's stalling, which is said to have frightened some drivers by suddenly stranding them in highway traffic without warning. According to Automotive News , 99 complaints were on file with NHTSA as of this morning.

Fiat Chrysler Automobiles has refused to comment on the issue to some media. Eric Mayne, a spokesman for FCA, told the New York Times that the company is aware of the problem and investigating, but that no injuries or accidents are connected to the complaints, as far as it knows.

In Windsor, Ont., where the Pacifica is a common sight because it is assembled in the city, there have been complaints on social media of the hybrid model stalling. One hybrid owner is said to have been stranded twice and had to be pushed out of traffic.

The complaints of the advocacy group, which was founded by Ralph Nader, make no mention of the hybrid, only the Pacifica in general. The group also said it had not been able to replicate the problem, nor had engineers at FCA, who have known about the complaints since April.

Sudden stalling is not an unknown automotive problem. Owners of the Ford Taurus and Sable made similar complaints dating back into the 1990s.  Last year more than 88,000 Ford vehicles were recalled to fix a problem with the fuel pump. Toyota, Volkswagen, Honda, Mitusbishi and Subaru have all dealt with stalling complaints within the last 24 months alone.

The Pacifica's alleged problem is confusing because it shares its Pentastar 3.6-liter V6 with many other cars in the FCA lineup, none of which are drawing similar complaints. Its nine-speed transmission is also shared with other vehicles and causing no known problems.