  We present a coherent timing analysis of the 2003 outburst of the accreting
millisecond pulsar XTE J1807-294. We find an upper limit for the spin frequency
derivative of 5E-14 Hz/s. The sinusoidal fractional amplitudes of the
pulsations are the highest observed among the accreting millisecond pulsars and
can reach values of up to 27% (2.5-30 keV). The pulse arrival time residuals of
the fundamental follow a linear anti-correlation with the fractional amplitudes
that suggests hot spot motion over the surface of the neutron star both in
longitude and latitude. An anti-correlation between residuals and X-ray flux
suggests an influence of accretion rate on pulse phase, and casts doubts on the
use of standard timing techniques to measure spin frequencies and torques on
the neutron star.
