SHANGHAI, China — China's passenger-vehicle sales reversed for a second consecutive month in September as weak economic prospects and a slumping stock market drove customers away.Domestic carmakers sold a combined 552,800 passenger cars, including sedans, sport-utility vehicles and multipurpose vehicles, which is a drop of 1.4 percent from a year earlier, the China Association of Automobile Manufacturers said.The decrease followed a 6.2-percent decline in August, which was the first year-on-year drop over the past two years.Potential auto buyers were held off by the 50 percent loss in the Shanghai Composite Index since the beginning of this year and record inflation, the highest in 12 years. The weaker economic outlook and higher fuel prices were also blamed for the market cooling.For the first three quarters of this year, passenger-vehicle sales rose 11.4 percent year on year to 5.1 million units.The rise marked a significant decline in growth, from the 17.1-percent increase for half-year sales and 23.8-percent jump for the same period last year, according to industry watchers.The drop also raised market concerns that the world's second largest auto market will not be able to achieve its full-year sales projection of 10 million units and maintain double-digit sales growth this year.Inside Line says: Some analysts believe the slowdown is a temporary setback for China's auto industry and that growth will average between 10 and 15 percent over the next five years. — Vivian Jin, Correspondent