TCC engaging too early

[joey]

Hey whats up B friends

I’ve got a 91 beretta base w/ 2.2 engine and a 3t40 3 speed auto tranny. My problem is when im driving through town going 20-25 mph, the TCC decides to lock up- almost like shifting a manual in too high of a gear at too low of a speed. So basically the converter is locked up and the car is in third gear going 20-25. Now this isn’t the classic TCC problem we bnet guys all know too well. (The lockup symptom when hot and stalls engine) I can let off the gas and it will disengage itself; but will immediately lock up again after applying gas. What is weird is that last winter I replaced the computer and the problem went away, it would engage at around 35 which seemed about right; the only drawback is that it contained the wrong memcal chip (it was for a 2.5 I think) The car ran but had missing issues. Transferred my old memcal to the new computer and the missing issue went away but the old TCC early lockup problem was back. Is this a MEMCAL issue or some kind of pressure switch in the transmission giving a faulty signal?

[1988GTU]

I think you can toggle switch the TCC, but I am unsure on your trans due to your year.  I toggled my TCC for my 88 and it worked great, I just had to be the relay.

[rweatherford]

I would say this could be a MemCal issue.  Hard to tell.

I guess the tranny is original and the speed sensor is fine.  You could check with a scan tool to see if the ECM is reading the same speed as the dash.