Function print with error

You would need to pass the vector always by reference, as you did correctly in the imprime() function. It seems that the error is in it, but in fact it occurred before and the vector is not correctly filled as expected. I would simplify the code like this:

#include <iostream>
#include <vector>
using namespace std;

void imprime(vector<int>& v) {
    for(int x = 0; x < v.size(); x++)
        cout << v[x] << " ";
}

void fibonacci(int x, int y, vector<int>& fi) {
    int z = 0;
    for (int b = 0; b < fi.size(); b++) {
        z = x + y;
        fi[b] = z;
        x = y;
        y = z;      
    }           
}

int main() {
    int valor1, valor2, numeroElementos;

    while (cin >> valor1 >> valor2 >> numeroElementos) {
        vector<int> numeros(numeroElementos);
        fibonacci(valor1, valor2, numeros);
        imprime(numeros);
    }
    return 0;
}

See running on ideone .

Change this:

void fibonacci(int x, int y, std::vector<int> fi, int numeroElementos);

so:

void fibonacci(int x, int y, std::vector<int>& fi, int numeroElementos);

And make the same change in function definition. Also, declare the vector numeros within while , look like this:

while (std::cin >> valor1 >> valor2 >> NumeroElementos) {
    std::vector<int> numeros;
    fibonacci(valor1, valor2, numeros, NumeroElementos);
    imprime(numeros);
}