  We present analysis of an XMM observation of the poor cluster AWM 4. The
cluster is relaxed and its X-ray halo is regular with no apparent substructure.
Azimuthally averaged radial spectral profiles suggest that the cluster is
isothermal to a radius of at least 160 kpc, with no evidence of a central
cooling region. Spectral mapping shows some significant temperature and
abundance substructure, but no evidence of strong cooling in the cluster core.
Abundance increases in the core, but not to the extent expected, and we find
some indication of gas mixing. Modeling the three dimensional properties of the
system, we show that ongoing heating by an AGN in the dominant elliptical, NGC
6051, is likely to be responsible for the lack of cooling. We also compare AWM
4 to MKW 4, a cluster of similar mass observed recently with XMM. While the two
systems have similar gravitational mass profiles, MKW 4 has a cool core and
somewhat steeper gas density profile, which leads to a lower core entropy. AWM
4 has a considerably larger gas fraction at 0.1 R200, and we show that these
differences result from the difference in mass between the two dominant
galaxies and the activity cycles of their AGN. We estimate the energy required
to raise the temperature profile of MKW 4 to match that of AWM 4 to be 9x10^58
erg, or 3x10^43 erg/s for 100 Myr, comparable to the likely power output of the
AGN in AWM 4.
