I took in to the shop. They diagnosed the problem as a faulty lockup solenoid. They replaced the solenoid, cleaned the screen and flushed the system. They flushed it only by removing one of the lines and replenishing the system until new fluid was running out. No power flusher was used.

On the way home it was still not going into lockup and the check engine light came back on. I took it back in this morning. They are confused and are now looking at the tranmission ECU as the possible cause of the solenoid failure. They are indicating that I will probably need a complete rebuild as it could be in the valve body or torque converter if the ECU checks out.

Garym: Could you send me the pages of the service manual that have to do with testing the transmission ECU. I have a 1990 manual and I bet it is very similiar but would like the right one. Could you also find out what RPM it is at when driving at 65mph in lockup?

Thanks for your help.