ODE15s not able to achieve the specified final time 'tf' in [t0 tf]

Hello,

I do have a set of ODE's which solves a chemical kinetics system. I am using some constraints to solve these equations and I am able to solve for few set of unknowns. However when I use more unknowns (~8) with 2 constraints to solve for rest 6 unknowns using ODE, I see the problem will not be solved till the final specified time. For e.g., I have specified initial time and final time as [t0 tf], which i pass to the ODE15s solver. So for the higher number of unknowns, the ODE solver will not solve until 'tf' has achieved (not blowing up as well). I have seen events being used to stop the code when steady state achieved, but I want something reverse. I want to know why the ODE solver do not finishes till the specified time! Can anyone help me why ODE solves only to a fraction of final time 'tf'? And also tell me how to fix this?

[Jan]

Without seeing any line of the code it is impossible to guess what's going on. What do you observe? Does ODE15 return and do you get any messages?