Ford 2003 Mustang Workshop Manual page 38

The equal distribution of weight on each side of the centerline, so that when the wheel and tire
assembly spins, there is no tendency for the assembly to move from side-to-side (wobble).
Dynamically unbalanced wheel and tire assemblies can cause wheel shimmy.
Engine Imbalance
A condition in which an engine's center mass is not concentric to the rotation center, causing
excessive motion.
Engine Misfire
When combustion in one or more cylinders does not occur or occurs at the wrong time.
Engine Shake
An exaggerated engine movement or vibration that directly increases in frequency as the engine speed
increases. It is caused by non-equal distribution of mass in the rotating or reciprocating components.
Flexible Coupling
A flexible joint.
Float
A drive mode on the dividing line between cruise and coast where the throttle setting matches the
engine speed with the road speed.
Flutter
Mid to high (100-2000 Hz) intermittent sound due to air flow. Similar to a flag flapping in the wind.
Frequency
The rate at which a cycle occurs within a given time.
Gravelly Feel
A grinding or growl in a component, similar to the feel experienced when driving on gravel.
Grind
An abrasive sound, similar to using a grinding wheel, or rubbing sand paper against wood.
Hiss
Steady high frequency (200-800 Hz) noise. Vacuum leak sound.
Hoot
A steady low frequency tone (50-500 Hz), sounds like blowing over a long neck bottle.
Howl