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 noise may be more noticeable in warm temperatures and may occur mostly at idle.
The NVLD (natural vacuum leak detection) module may make a thump/rattle noise during the normal purge of the EVAP canister. The noise only occurs when vapor purge is active and stops when the EVAP canister purge valve is closed.
If the customer’s vehicle exhibits this concern, Ford recommends replacing the NVLD module assembly.
AE8Z-9J279-L............NVLD assembly (4-door)
AE8Z-9J279-M..........NVLD assembly (5-door)