ABS problem 1996 Discovery

[rdrinkward]

I have a 1996 Discovery 1 with 144,000 miles. I am experiencing problems with the ABS system. Under normal driving conditions "driving on smooth paved surfaces ", occasionally the ABS system will kick in when trying to stop the vehicle. When this occurs the brake pedal "for lack of a better description" pulses. The pulse is definitely not from the rotors. It sounds and feels like a spring is under the brake pedal "boing...boing...boing". Does this sound like a faulty ABS Modulator Shuttle Valve, ABS Modulator, or the ABS Controller?