That may be an ignition switch problem but also may be something broken in the steering column. The electrical part of the switch is mounted to the top of the column farther down. It's connected to the lock by a couple of sliding gears and a rod that could have problems or the ignition lock itself could be broken. Your probably going to have to remove the lock itself for inspection as a starting point.
REMOVAL & INSTALLATION
See Figure 1
STANDARD STEERING COLUMN
Disconnect the negative battery cable.
Remove the left-side lower trim panel.
Remove the steering column-to-support screws and lower the steering column.
Vehicles equipped with floor shift and automatic transaxles use an ignition switch inhibitor and park lock cable. On these models the park lock cable must be disconnected from the ignition switch inhibitor, by releasing the locking tab, before removing the column.
Detach the dimmer switch and turn signal switch connectors.
Remove the wiring harness-to-firewall nuts and steering column.
Remove the steering column-to-steering gear bolt and the steering column from the vehicle.
Remove the combination switch, as outlined in this section.
Place the lock cylinder in the RUN position.
Remove the steering shaft assembly and turn signal switch housing as an assembly.
Using the Terminal Remover tool No. J-35689-A or equivalent, disconnect and label the wires "F" and "G" on the connector at the buzzer switch assembly from the turn signal switch electrical harness connector.
Place the lock cylinder in the RUN position and remove the buzzer switch.
Place the lock cylinder in the ACCESSORY position. Remove the lock cylinder retaining screw and the lock cylinder.
Remove the dimmer switch nut/bolt, the dimmer switch and actuator rod.
Remove the dimmer switch mounting stud (the mounting nut was mounted to it).
Remove the ignition switch-to-steering column screws and the ignition switch.
Remove the lock bolt screws and the lock bolt.
Remove the switch actuator rack and ignition switch.
Remove the steering shaft lock and spring.
Fig. 1: Exploded view of the ignition lock cylinder - 1988-90 vehicles
Observe the following tightening specifications when installing. Tighten the steering lock screw to 27 inch lbs. (3 Nm), the dimmer switch stud to 35 inch lbs. (4 Nm), the turn signal switch housing screws to 88 inch lbs. (10 Nm), the turn signal switch screws to 35 inch lbs. (4 Nm) and the steering wheel lock nut to 30 ft. lbs. (41 Nm).
To install the lock bolt, lubricate it with lithium grease and install the lock bolt, spring and retaining plate.
Lubricate the teeth on the switch actuator rack. Install the rack and the ignition switch through the opening in the steering bolt until it rests on the retaining plate.
Install the steering column lock cylinder set by holding the barrel of the lock cylinder, insert the key and turn it to the ACCESSORY position.
Install the lock set in the steering column while holding the rack against the lock plate.
Install the lock retaining screw. Insert the key in the lock cylinder and turn the lock cylinder to the START position and the rack will extend.
Center the slotted holes on the ignition switch mounting plate and install the ignition switch mounting screw and nut.
Install the dimmer switch and actuator rod into the center slot on the switch mounting plate.
Install the buzzer switch and turn the lock cylinder to the RUN position. Push the switch in until it is bottomed out with the plastic tab that covers the lock retaining screw.
Install the steering shaft and turn signal housing as an assembly.
Install the turn signal switch.
The remainder of installation is the reverse of the removal procedures.