1990 Honda preluid si 2.1 litter also four wheel steering

Maybe some more information from you would help. Does it do it below that speed or does it shake at idle. If it shakes at the higher speed it could be a simple thing like a balance problem on a tire or a bad cord in a tire. I would try rotating the tires to see if the problem shifts location like to the rear. If not, possible alignment issue or a motor mount problem is another possible.

Just as a though, if it has been rainy and or muddy, wash the front wheels real good on the inside and outside of the rims. Dirt buildup or deposits will drastically throw a vehicle's wheels out of balance. Look at this FIRST.