95 626 130k 4banger auto. Got back from a 2500 mile trip and all was fine. Was due for all the fluid changes again so off I went. After about 500 miles the lock up started acting up. When on the highway if you were going up a slight hill and the car went out of lock up to maintain speed it will not reengage the lock up. You have to give it throttle to down shift then let it reupshift then it will lock up again. This can get quite annoying depending on where you are driving. Old trans fluid was fine (no metal or anything abnormal about it) was just due to be changed. (I am very good about maitence on my cars, all fluids get changed every 30k (motor oil a little more often lol)). New fluid still looks fine.

Any ideas?

 

The lock up is part of, and inside the torque converter and may not be getting the signal that it requires, or it's clutch may be going bad.
I am not sure what activates the lock up in these cars, but it may be the PCM/ECU that tells it when to do so.
Have you tried resetting the ECU by disconnecting the battery for a time (+/-1/2 hr) then reconnecting it to see if that solves the problem?
My guess though is that w/that many miles on the car, it may just be time for a new TC.
Also as a point of refernce, a 95 is going to have the OBDI system. (<"96)