Stalling/No Power in First
 

Girlfriend has a 1999 Camaro with the 3.8L and automatic transmission that we got her back in August.

Girlfriend starts the car in the morning (Kansas, so it's pretty chilly) and lets it sit for 1-2 minutes before backing out then putting it into drive. However, every now and then the car will just stall going from reverse to drive. When I drove it about a week ago, it finally did it to me. Twice actually. Furthermore, when trying to drive it I noticed it had no power when trying to go up a slight hill. Tried putting it all the way into 1st and same thing. Almost like it is stuck in 2nd/3rd or something. However, after successfully getting it to move enough to shift into "second" it drives fine from then on. It doesn't always do this, but may be linked to how cold it is out.

Ideas?

first i would suggest having the car/computer scanned for trouble codes. you should be able to have it done at just about any auto parts store. if there are any codes write down the code/s and let us know what they are. it could be the trans is getting stuck between gears so a trip to a trans shop may be in order. it does take a speacial scanner to read trans trouble codes so the parts store scanner will not show

Assuming you have no codes.

Step one: is all the normal maintenance up to date? Plugs, plug wires, fuel and air filters. How do the vacuum hoses look? Replace anything that looks hard, worn or cracked. This would be the normal 100K check.

After that I would clean and re-home the IAC and I would clean and test the EGR valve. Re-torque the intake and throttle body. After that you are going to need a good mechanic with the right equipment.

There are many issues that first show up as a rough idle/stalling in their early stages. At this point you can not even be sure if this a fuel injection/ignition/engine issue. Issues can be very hard to find in their early stages, once it gets worse they become easier to find.

datalog it to a computer and see if the torque converter is locking/unlocking.
If a tc remains locked, the car will stall when put into gear at idle speed. It will also stall when coming to a stop.

A bad tc may also feel like you are starting in 4th gear even at 10mph

just one more thing for you to check