[RFI] Unknown RFI from truck when in motion but in neutral

[David Jordan]

Hi Folks,

Found an interesting problem while listening to AM 630 all news station 
here in WDC.


Getting loud clicking noise.  Sounds very much like spark plug noise but 
when coasting at 30mph and placing the engine in neutral such that the 
engine RPM drops from 2500rpm to idle, the ticking noise remains at 
speed.  However, as the vehicle slows down the noise also slows down.  I 
can rev up the engine while it remains in neutral but the speed of the 
noise doesn't change.  Is there some type of speed or other monitoring 
devices on the wheels of the 2001 Explorer that is sending RF signals to 
the on-board computer?  This one is got me scratching my head.

thoughts,
dave
wa3gin