[maramizo]

Then get a new engine, ha. ha. ha.
No honestly, this should fix it.

pawn Код:

if(strcmp(cmd, "/engine", true) == 0)
    {
        if(IsPlayerConnected(playerid))
        {
            if(IsPlayerInAnyVehicle(playerid))
            {
                if(GetPlayerState(playerid) != PLAYER_STATE_PASSENGER)
                {
                    GetPlayerName(playerid, sendername, sizeof(sendername));
                    if(gEngine[playerid] != 1)
                    {
                        SCM(playerid, COLOR_PINK, "Car engine started.");
                        new engine, lights, alarm, doors, bonnet, boot, objective;
                        GetVehicleParamsEx(pveh, engine, lights, alarm, doors, bonnet, boot, objective);
                        SetVehicleParamsEx(pveh, 1, lights, alarm, doors, bonnet, boot, objective);
                        gEngine[playerid] = 1;
                        engineOn[pveh] = 1;
                        format(string, sizeof(string), "%s starts the car's engine.", sendername);
                        ProxDetector(30.0, playerid, string, COLOR_PURPLE,COLOR_PURPLE,COLOR_PURPLE,COLOR_PURPLE,COLOR_PURPLE);
                        return 1;
                    }
                    else if(gEngine[playerid] == 1)
                    {
                        SCM(playerid, COLOR_PINK, "Car engine stopped.");
                        new engine, lights, alarm, doors, bonnet, boot, objective;
                        GetVehicleParamsEx(pveh, engine, lights, alarm, doors, bonnet, boot, objective);
                        SetVehicleParamsEx(pveh, 0, lights, alarm, doors, bonnet, boot, objective);
                        gEngine[playerid] = 0;
                        engineOn[pveh] = 0;
                        format(string, sizeof(string), "%s stops the car's engine.", sendername);
                        ProxDetector(30.0, playerid, string, COLOR_PURPLE,COLOR_PURPLE,COLOR_PURPLE,COLOR_PURPLE,COLOR_PURPLE);
                        return 1;
                    }
                }
                else
                {
                    SCM(playerid, COLOR_CREAM, "You cannot start the engine as passenger.");
                    return 1;
                }
            }
            else
            {
                SCM(playerid, COLOR_CREAM, "You are not in a vehicle.");
                return 1;
            }
        }
    }

EDIT:
I would suggest storing the gEngine onto the vehicleid, instead of playerid.