[Threshold]

You should try using player vehicles instead, so assign them to a playerid.

pawn Код:

new veh[MAX_PLAYERS];

public OnPlayerConnect(playerid)
{
    veh[playerid] = -1;
    return 1;
}

public OnPlayerDisconnect(playerid)
{
    if(veh[playerid] != -1)
    {
        DestroyVehicle(veh[playerid]);
    }
    return 1;
}

COMMAND:car(playerid,params[])
{
    new model, carc1, carc2;
    new Float:x, Float:y, Float:z;
    if(sscanf(params, "iii", model, carc1, carc2)) return SendClientMessage(playerid, RAUDONA, "/car [model_id] [color1] [color2]");
    GetPlayerPos(playerid, x, y, z);
    if(veh[playerid] != -1)
    {
        DestroyVehicle(veh[playerid]);
    }
    veh[playerid] = CreateVehicle(model, x, y+5, z+2, 0, spalva1, spalva2, 400);
    TrDegalai[veh[playerid]] = 8.0;
    SendClientMessage(playerid, BALTA, "Car created!");
    return 1;
}

EDIT: At the end of CreateVehicle, there is a respawn delay parameter, you just need to set this to -1 to prevent it from respawning.
https://sampwiki.blast.hk/wiki/CreateVehicle