Runge-Kutta 2nd and 4th order
 

Hello,
I program solver for Burgers equation, Shallow water and Euler equations. Everything works good, but one thing not - 2nd and 4th order Runge-Kutta method. I get bigger error with 2nd and 4th order RK method than with Euler method. I tested methods on ODEs and everything is good, but for PDEs not :-(.

Don't you know where can be error? Or is there anyone, who could help me via email and look on my code?

Thanks for any advice.
Jakub