  I study the possibility that within the frame of the core degenerate (CD)
scenario for type Ia supernovae (SNe Ia) the merger process of the core of the
asymptotic giant branch (AGB) star and the white dwarf (WD) maintains an
envelope mass of ~0.03Mo that causes a later helium shell flash. I estimate the
number of pre-explosion helium shell flash events to be less than few per cents
of all CD scenario SNe Ia. A helium shell flash while the star moves to the
left on the HR diagram as a post-AGB star (late thermal pulse; LTP) or along
the WD cooling track (very LTP) causes the star to expand and become a born
again AGB star. Merger remnants exploding while still on the AGB form
{hydrogen-polluted} peculiar SNe Ia, while an explosion inside an inflated
born-again star results in an early flux excess in the light curve of the SN
Ia. The fraction of systems that might show an early flux excess due to
LTP/VLTP is <(few)x10^{-4} of all SNe Ia, much below the observed fraction. In
the frame of the CD scenario SNe Ia with early flux excess result from SN
ejecta collision with planetary nebula fallback gas, or from mixing of 56Ni to
the outer regions of the SN ejecta. Ongoing sky surveys might find about one
case per year where LTP/VLTP influences the SN light curve.
