please configure local identity and proxi identity
set security ipsec vpn vpn-name ike proxy-identity local y.y.y.y/8 remote x.x.x.x/24 service any
and please check on the firewall ASA access list allow that particular subnet remeber.
It should work , and if it is not work go for the following option:
1. In some cases i have seen traffic drop due to policy logs (init -close ) option so remove it and check.