Very odd trans issues?

My wife has a 2002 Jeep Liberty with the 3.7 and an auto trans. It's got 122k trouble free miles. Recently it's had an issue that's had me at a loss. The hard part is, my wife is giving me the problem description, but I can't replicate it, and neither can our mechanic. Here's the issue:

She first noticed that when at a stop sign or stop light, her jeep would surge a bit. The first time it happened, she thought someone had tapped her from behind. The same day, she was driving home from work on the highway, and said that her engine was revving higher than it should, and it felt like the car was working harder to attain highway speed. She pulled over because the engine was revving, put it in park, and the engine continued to rev with her foot off the gas, and the car in park. She shut it off and called me. I drove out, turned the truck back on and everything was perfect. Had it towed to our mechanic friend, and he couldn't replicate it either. I had him change the fluid and filter in the transmision. He noticed a miss at idle, and recommended changing the plugs, air filter, and said the battery was on its way out too. When I got the truck back I replaced battery, plugs, and airfilter per his suggestion. When I was changing the plugs I noticed the two hoses attached to the sides box over the throttle body were cracked causing a likely vacuum leak. I replaced these hoses, and the miss went away.

The mechanic ran OBD2 diagnostics on the whole vehicle and gave it a clean bill of health. Everything's been fine for the past two weeks. Yesterday she called me and said her jeep just seemed to be working harder on the highway again. She pulled over, power-cycled the engine, waited a few minutes and drove it home.

So there's only a few things that I can think of that woulc cause such a cryptic issue:
First, some unseen vacuum leak somewhere which is causing running issues
or
The lockup in the torque conerter. I'm thinking the converter might not be locking all the time on the highway causing more slip and more revs, and not unlocking correctly at a stop causing the surging.

Has anyone else every experienced anything like this? I can't seem to replicate the problem. Are there any electronics or sensors that could fail and cause this issue? Is the converter electronically locking?

Honestly I'm at a loss. I hope this isn't a sign of a failing auto trans. My wife is a very conservative driver, and never beats on the vechicle at all.

Sorry for the novel, and thanks in advance,

-Matt

It is not a "car",Welcome to the site. Does it give a code,check engine light? I think I would have a trans flush,filter change done at a dealer,it comes with warranty. Just a thought.

No codes, no CEL's, nothing popped up with the OBD scanner. We already had the trans fluid and filter changed, problem persists.

Sorry for the car comment, and thanks for the welcome. I've been a lurker here since my wife got her KJ 3 years ago. Since then I picked up a TJ, dad's got an XJ and my sis even bought a ZJ. We love us some Jeeps!

-MK

I know this might sound completely stupid but it did happen to my wife when she drove my jeep once. She put it into second instead of drive. Scared the crap out of me when she got home and wondered why it ran so hard. Also I have dropped it out of overdrive before and that made it run very high RPMs on the highway. Just some suggestive thoughts to get the brain juices flowing!

Oh yeah and Welcome!!!!!!

So I dusted off my factory shop manuals this morning and dug into the Transmission Diagnostic Procedures manual. I found a few interesting things.

First it talks about an Orderly Shutdown Procedure in which it recognizes some fault that doesnt require immediate shudown, and defaults the trans to 3rd gear if you're at speed. This could explain some of the issues with higher revs that my wife is experiencing if the trans locks O/D out.

Second it talks about a stuck AIS or a dirty TPS being the potential source of some issues that might disengage the EMCC (Electronically Modulated Converter Clutch). I'm also wondering if a sticky IAC could cause some issues here...

The issue seems to happen on hot, humid days when she's got the A/C on. I'm wondering if it's seeing a slight overtemp which is enough to send the TPS into a shutdown mode without throwing a code.

Any suggestions? Is dealership service the only solution? I want to make sure if I take it to a dealership, I have some idea of what's wrong.

-MK

p.s. trans was definately in D. I asked all the obvious, insulting questions first. I.E. is your floormat jammed under the pedal, are you driving in heels, etc.

For the overdrive possibility make sure she also didn't bump the O/D lockout on the shifter when putting it into gear or resting her hand on it, etc.. Sounds silly but it wouldn't be the first time it happened to someone.

Seems to me if its coinciding with using the air on a hot day it could be heat related. Did the trans temp light ever come on? Look and see if the radiator needs to be blown out, buildup of dead bugs etc. Does the engine temp run above the halfway mark on the gauge?

Maybe a a cadalitic coverter geting hot and slowing flow doging it down and revs are from it trying to keep its self running you think it would show a code but odd things can happen.
Just an idea you might want to check

I was having similar problems before swapping out my transmission(and torque converter). It started acting funny at times on the highway, but the biggest problem was that it(the TC) was staying locked up when I came to a stop, sometimes surging and sometimes stalling. It got worse and worse and I picked up a trans/TC from a salvage yard for $250 and everything has been fine since, aside from a random hard 2-3 shift.

Did you try replacing the control module, it is a $40 replacement. I forgot exactly what it was but it had me revving at 4k on highway with complete loss of power.

My cousin's '00 Grand Cherokee had a problem like that. It would go into a higher gear and idle bad and seemed like it had a trans. that was trying to go bad. It turned out to be his TPS which was a $30 part from the part store and I changed it easily in about half an hour. He has the 4.7l V8 which if I am not mistaken is what the 3.7l is based off of.