Viscosity of liquid interrupts accuracy of micropipette? Does viscosity of liquid interrupt accuracy of micropipette?

I would like to dilute 85% $\ce{H3PO4}$ acid to $\pu{1.194 mol/dm3}$ so I had to pipette 366 microliter into 4.634 mL of water. Then, I adjusted the pH to 11 by dropping 25% $\ce{NH3}$ solution. I did 4 times but final volume was not equal (about 50, 50,100, 200 mL). I think the problem is viscosity of liquid when I pipetted concentration acid.
I think you try to use glass pipette instead. It may decrease viscosity effect.