29.05.2014, 13:18
Looks like you have the engine variable wrong. GetVehicleParamsEx will show engine as 1 when its running and 0 when its off, so it keeps starting the engine with your code.
https://sampwiki.blast.hk/wiki/GetVehicleParamsEx
https://sampwiki.blast.hk/wiki/GetVehicleParamsEx