My car has been doing this for awhile and haven't figured out what is causing it. When going about 35mph and accelerating to 40mph, the converter locks up and will stay locked up as long as you don't let up on the accelerator. If you let up it will disengage. I've checked the T/V cable and it appears to be set OK, has just a tiny bit of slack in it.
I also noticed on a long road trip last week that it was disengaging and engaging with slight movements of the accelerator pedal at 70-80mph. On the way home it acted fine, it stayed engaged at highway speeds all the time like it should.
Transmission fluid level is Ok, fluid is not burnt, shifts gears fine. Right after I got the car I found the switch busted at the brake pedal for the converter lockup busted and probably hasn't worked for years. I have it jumped out until I can get another switch.
Will playing with the T/V cable adjustment help or is this all computer command?

 

its all computer. when my converter switch went out it would shuffle in and out of lockup every 3 seconds.

 

Is the converter switch part of the ECM or is it a seperate device?