New Delhi, October 11: With the beginning of the festive season, the sales of vehicles have shown little improvement but the trouble of automobile industry is not over, at least data suggests so. The sale of passenger vehicles slumped 23.7 per cent year-on-year in September to 2,23,317 units, while passenger car sales dived 33.4 per cent to 131,281 units making it the 11th straight month of decline. In the year-ago period, passenger vehicle sales stood at 2,92,660 units.