Here are the steps involved in changing the torque converter solenoid on a 1990 Cavalier:
1. Disconnect the negative battery cable.
2. Remove the battery and battery tray.
3. Locate the torque converter solenoid on the side of the transmission.
4. Remove the two bolts that hold the solenoid in place.
5. Carefully remove the solenoid.
6. Note the position of the solenoid so that you can reinstall it correctly.
7. Install the new solenoid.
8. Replace the bolts that hold the solenoid in place.
9. Reinstall the battery and battery tray.
10. Reconnect the negative battery cable.
Once you have completed these steps, the torque converter solenoid will be changed and you can start your vehicle.