Feels like convertor is stuck locked up?

[2QUIK6]

Update: Feels like convertor is stuck locked up?

This started happening yesterday on the TTA. When driving around town about 20-35 mph, the car is surging in 3rd gear. Feels just like the GN does when I forget to turn off the manual TCC lockup switch.
If I accellerate pretty moderately to heavy, it runs great. But light accel and decelleration, it surges.
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What should I check/replace. I see some posts about the TCC solenoid being stuck, but where is this if that's what I need to look at. I know nothing about transmissions except how to change the oil/filter.
Thanks

 

[2QUIK6]

Ok, I see where the TCC solenoid is and how to replace it, no big deal.... What I don't understand is how to test to see if that is in fact the problem.
I've read about going 50mph and lightly pressing the brake, if its working correctly, the rpms will rise slightly when brake depressed. Also, the car has to be to full op temp for this to work. But if the solenoid is stuck, wouldn't it stay locked up no matter what? It seems to work ok when cold.
If I unplug the wiring harness, and the problem goes away, that could be electrical, or could it still be the solenoid, if its never engaged because the wires are unpluged, then it can't get stuck...correct??
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Can someone explain how to test this darn thing?
Thanks

 

[MeanBuicks]

Two of the tests you mentioned are good for diagnosing your problem.

First, unplug the harness while the vehicle is cold. As you stated, this will prevent the TCC from applying at all. If the symptoms do not reoccur, good chance that the TCC solenoid was sticking on you.

To further confirm this, the brake pedal test is good. Applying the brake pedal cuts the voltage from the apply circuit. If the converter remains locked with the pedal depressed, rest assured the solenoid is sticking.

It happens to all of these 200s, regardless of mileage. I even replaced a sticking solenoid on an 8000 mile GNX.

 

[2QUIK6]

Thanks for the clear info Greg, I'll test it tonight after work.

 

[2QUIK6]

Update: It would not do the same thing again today! I drove it about 7-10 miles, did the 50mph test, and the TC did unlock and lock back up, but several times it didn't seem to make the rpms rise/fall very much as it did when cold. It does seems to be in 4th gear sometimes at too low of a speed, like 30mph.
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I guess the TCC solenoid could be partially stuck sometimes and be intermittenly stuck??