I was given a 2001 Camry (4spd auto) by my grandfather last fall, the car has close to 190,000km (most of which are grandpa miles)
when I went up to move the car last time, it hadn’t had a battery in it for close to six months. It started really hard and ran quite badly, I thought it may be old gas or the air filter, but once the car was in gear, you almost had to neutral drop it to keep it running. The motor is severely underpowered and being a student, I’m unable to spend a lot of money on the car, it has been sitting in a barn for close to a year now and I had heard that If the battery was out of the car for long enough, that the ECU would reset and If there was carbon build up on the IAC or the throttle body, then the car would run rough, the car is also two hours away from where I live, so when I go up next time, I want to have everything that it may need with me. Am I just beating a dead horse with the possibility of the carbon in the throttle body or is it a possibility?

 

Disconnecting the battery can cause idle issues. This normally self corrects after a few start ups.

Ethanol fuel breaks after about 3 months. It also absorbs water via moisture in the tank.

Carbon in the throttle body might effect idle but in mild way, not what you are experiencing.

Visually inspect the engine vacuum hoses, wiring, ignition system wire for signs of damage from mice, etc.