Torque Convertor Lockup

[csxtrainman]

Been putting it off, but ive been needing to check out why my 91 isnt locking up. Tonight tho, the trans locked up fine a few times, then didnt do it anymore the rest of the way home. Does this indicate a broken wire somewhere along the way, or do the lock up solenoids kinda sorta work before they completely die? If it is the solenoid, how much does one run from Ford?

Thanks guys

 

[MrShorty]

Sounds like an electric fault. I'd start by getting a wiring diagram, so you can see how the TC lockup control circuit is laid out. The PCM acts as a ground side switch.
Then some basic electrical checks. Do you consistently have 12 V at the B+ wire to the solenoid? Continuity through the solenoid? Wiring from transmission to PCM look good?
Then run EEC-IV KOEO test to enter output state test. While monitoring voltage drop across the solenoid, see if the PCM can switch the solenoid on and off. Wiggle wires and such to see if you can locate a bad connection.
If you get to this point, do a road test. While monitoring the voltage drop across the solenoid, drive the vehicle and see if the PCM tells the TC to lockup.
See where that gets you.

 

[Opera House]

What wasn't mentioned

The TCC solenoid is mounted on the valve body and can not be replaced without removing the valve body. There is a keeper that must be removed from the back. Don't attemp this without a manual as a number of parts will pop out without any indication of where they go. Also suggest you replace the body gaskets with the double thickness ones in case there is any warping. Not that hard, just need the $16 manual from www.bulkpart.com and the solenoud is about $50. Go to tech bull on www.atcdg.com I think they have a note on the screen clogging on the solenoid. Could be the 3-4 solenoid that has the screen.