OK, your question is a bit vauge, and there are missing bits, i.e. the start point for y.
I'm assuming you are trying to solve a control problem. As mentioned above, you need to carefully look at dimensions, and I think you want the matrix exponental function, expm, (don't forget the "m").
I started my simulation below at some random point.
AF= [ 0 1 0 0;
0.00010714 0.00275 10.049 0.98385;
0 0 0 1;
-7.6531e-05 -0.0019643 -0.17761 -0.70275];
Y = randn(1,4);
Y(i,:) = expm(AF*t(i))*Y(i-1,:)';
Of course if you have the control toolbox, there are many better ways to do this, e.g.
G = ss(AF, zeros(4,1), eye(4,4), 0)
Y0 = randn(1,4);
[Y,t] = initial(G,Y0,t)