1D counterflow pressure stepping instability?

[Chris N]

I'm wondering if it even makes sense to try and run the 1D counterflow solver for ideal gas cases with very high pressures (something like 60 MPa). Obviously gases are supercritical at such pressures and the ideal gas assumption would generate deviations from reality. I was surprised though that I had trouble even stepping the solution up into that pressure regime. I've attached a script that attempts to walk up the pressure and when it fails it writes out the temperature field. It doesn't look like the flame is particularly thin, which is what I thought might have been happening as the pressure increased. Also attached is the solution right before the solver failed to converge.