Ford MAFs

[James W. Swonger]

 Burn-off is where the computer forces a period of high current on the
wire, gets it hot enough to vaporize most substances (except platinum)
in order to expel any residue. The Bosch system does this on every
engine shutdown.

 I imagine that to do without this, they must do some sort of auto-cal
sequence, where they see a change in current at resistance vs known change 
in air flow, and use that as a baseline, rather than presuming a fixed 
dI/dF over the life of the sensor, which is what the burn-off is supposed
to maintain.