Some 2011-2013 Ford Fiesta vehicles built on or before 9/12/2012 may exhibit a thump/rattle noise coming from the fuel filler neck area.
The customer may indicate that the noise is most noticeable in warm ambient temperatures, and that the issue may be intermittent and may occur mostly at idle.
The Natural Vacuum Leak Detection (NVLD) module may make a thump/rattle noise during the normal purge of the evaporative emission canister (EVAP). The noise only occurs when vapor purge is active and stops when the EVAP canister purge valve is closed.
Replace the NVLD module assembly. Refer to workshop manual section 303-13.
AE8Z-9J279-L………..NVLD assembly, 4-door
AE8Z-9J279-M……….NVLD assembly, 5-door