Volvo Repair: 1995 volvo turbo wagon noise, cpu failure, brake rotors

Question
Hello,
I just purchased a used volvo turbo wagon from a private party.
My wife says that when she drives it for long period of time 25
-100 miles and she slows down  to make her fist stop, the whole
car shakes for 1-5 seconds. I looked the wagon over checking
and found nothing apparently wrong. The engine dosent have
leaks, the sparkplugs look healthy, and break system seems
normal. I am wondering if this could be the turbo or engine cpu
failure. No oil on the plugs so I assume all 5 cycls are hitting
fine. The engine is nice and quiet and the idle is steady under
1000. Transmition shift real smooth. Do you have any idea what
could be causing this?

thank you for your input.  

Answer
Hello Marc,  There only two things that will make that car shake ,suspension or brakes.And in aged and overlooked car,both.One to five seconds is significant time.The only thing that fast is the ABS or your speed before slowing down.You and your wife need to take her on a road test together to better understand the condition.Waped brake rotors can have the same effect due to a certain pedal pulsation ,rapid up and down motion.Sometime there is a shaking of the sterring wheel at the same time.Worn out ball joints,need to be checked,Tires themselves should checked.Has ABS lite been on,if so have the codes checked.Thank you and good hunting!  PKD