Possible Torque converter issues?

[BLK3]

Have an 03A with a Dennis R. tune, Car acts really strange with AC on: it has what seems to me very high rpm fluctuations while in drive [Aprox.300 rpms]. Is noticable at all speeds but especially when coasting or driving slowly as car noticably speeds up. Does not due this with AC off. I Know that cars at one time had a method of increasing idle speed when compressor kicked on but was never this apparent. Also does some strange things of similar nature with stock tune in and AC on, so its probaly not in tune. Any of you knowlegeable folks out there got suggestions? Thanks , The reason for suggesting that it may be a torque converter issue is that yesterday while driving on the hwy. it seemed as if the TQ never locked up while running at highway speeds until car was parked for a short period and then redriven over the same stretch of hwy. where it drove normally, prior to starting this short trip transmisson seemed to shift much firmer than normal under light throttle on the 1-2 shift.

[lecantotaylor]

When was last time you changed the tranny fluid? How many miles on your car? Perhaps a full flush at the dealer ($$$) or DIY partial drain/refill of 5 quarts at tran-cooler line, done a couple times a few hundred miles apart, will refresh the fluid enough to cure the problem. Make sure you only use Mercon V

[mpearce]

Could it just be lock up? Locking, unlocking?

[offroadkarter]

Put the stock tune back on and tell us if it does the same thing.

[Windsor58]

Mine does that. even in park. I have two separate things, though. First seems to be the AC. Idle and while driving there is a small 200-400 jump when the AC kicks in or out. Second is - I have 4.10s, a 3k stall TC and the TC locks and unlocks with little load on the highway. It will unlock when the AC kicks on, even. I bought the software to try to adjust the TC lockup parameters, but haven't been able to get the software working, yet. I am hoping that will solve the lock/unlock so I can get a little better mileage. Next time I have to take it to the dealer, I am going to have them check the AC. It also makes a pretty loud noise when the AC clutch locks up (AC compressor come on).
+1 on doing a trans service, though. Cheap insurance even it if doesn't solve the problem.

[merc]

Lock-up converters also contain a friction clutch that locks the converter impeller to the turbine, usually in higher gears. A solenoid-controlled oil passage, commanded by the car’s powertain control module (PCM), locks and unlocks the converter based on driving conditions. Could you give us more information about your transmission maintenance schedule, mileage, and driving style. A quick call to DR might also yield some other options. It might be time to re-build your tranny.

[ctrlraven]

I noticed mine kind of doing the same thing, but it does the rpm drop as I have read about on here with high stall converters. It ONLY does it when the A/C is on and I take my foot off the gas above 50mph if I coast. With the A/C off it does not happen at all.