2014 v6 6r80 issues

[DK_Busan]

Hello again from South Korea!

It seems to be two separate symptoms, although I'm not 100% sure—they might be related.

Symptom #1 — Happens only when fully cold & moving for the first time

After a full cold start, I let the engine warm up completely until the RPM settles to normal idle.

Then, as I begin driving:

• In 1st gear, if I accelerate up to about 1200 RPM and then release the throttle, the car starts surging / jerking, bouncing between 900–1200 RPM repeatedly (like "boong-boong-boong-boong").
• This only happens when the car is moving.
• There is no issue in Park or Neutral—RPM falls smoothly there.
• And interestingly, it does NOT happen in manual (select-shift) mode. When I manually hold 1st gear and lift off the throttle, everything is normal.

Symptom #2

When the transmission is warm (especially after a long drive):

• In 1st gear, if I accelerate to around 1100–1300 RPM and release the throttle, the RPM hangs for 15–20+ seconds before slowly dropping.
• Once the car shifts into 2nd or higher, the RPM behavior is completely normal.
• Again, this symptom also does not occur in manual mode—RPM drops normally there.

Additional notes

• No DTCs or warning lights.
• Transmission fluid + filter were replaced, and fluid level properly set.
• Intake leaks checked (none found).
• MAF sensor replaced.
• Multiple ECU resets / relearns attempted.
• Symptoms remain identical.

Summary

Both problems only happen in automatic mode, while manual mode behaves normally, which makes me wonder if it's related to:

• torque converter behavior
• a sticking solenoid
• valve body logic
• throttle/airflow control specific to auto-shift tables

If anyone with 6R80 experience has seen similar behavior or can point me in the right direction, I'd really appreciate it.