ABS working when it shouldn't

[Myke456@aol.com]

During the past 12 years I've spent in my 87 5kcsTQ, I've fixed a few minor 
ABS related problems. In all these circumstances the ABS OFF light 
illuminating (and shutting off the system) always clued me, that a problem 
existed.

Current problem happens intermittently:
While driving, when I apply the brakes the pedal will feel stiff and high 
(hold on-don't jump to the bomb answer just yet), while I can hear/feel the 
ABS system working against my foot, and the car barely slows down. Increased 
pressure will sometimes "release" the working ABS and normal braking occurs. 
The ABS OFF light does not illuminate. In essence, the ABS system seems to be 
keeping braking from occurring when it shouldn't be. Braking works normally 
when the ABS is switched off manually. 

Consider the following:
above driving 20 -40 mph, dry paved road
bomb is a few years old, but takes 30+ pumps before stiffening the pedal
master cyl less than 6 mo. old
sensor caps recent and positioning OK

I don't recall a problem like this posted to the list in the past. Any ideas?

  ([____]=====OOOO=====[____])   87 5kcsTQ, 242k miles
	 Mike Aiello     original owner      Dutchess County, NY