[Scenario]

pawn Код:

CMD:eon(playerid, params[])
{
    if(LoggedIn[playerid] == 0)
        return SendClientMessage(playerid, COLOUR_GREY, "You must be logged in to use this command.");
    if(!IsPlayerInAnyVehicle(playerid))
        return SendClientMessage(playerid, COLOUR_GREY, "You are not in a vehicle.");

    GameTextForPlayer(playerid, "~g~Engine starting...", 2500, 5);
    SetTimerEx("EngineOn", 3000, false, "i", playerid);
    return 1;
}

forward EngineOn(playerid);
public EngineOn(playerid)
{
    GameTextForPlayer(playerid, "~g~Engine started!", 1500, 5);
    new vehicleid = GetPlayerVehicleID(playerid);
    GetVehicleParamsEx(vehicleid, engine, lights, alarm, doors, bonnet, boot, objective);
    SetVehicleParamsEx(vehicleid, 1, lights, alarm, doors, bonnet, boot, objective);
    return 1;
}

See if this works for you.