Wipers are loose on corolla 99

What, they work when NOT activated?

I presume you mean a) the wiper arms can be moved by hand; and b) they don't move when you turn on the switch.

The wiper arms are connected with a rod system to the wiper motor with cheap ball and socket bearings, which wear out and disconnect themselves. You access the system by removing the air intake panel in front of the windshield. Sometimes you can simply snap them back into position, but if the wear is too great, they come off again. The wiper arm pivots may also be partly seized. Check with Toyota on the cost of the wiper rod and arm pivot assembly.

SD