02 alero stalling problem?

ok guys i need help, im trying to fix my girlfriends 02 alero it has a 2.2 4cyl engine in it, put another motor in it and now it wants to stall all the time i took it to autozone and they told me it was the camshaft sensor or something of that nature. so i ordered one and put it on, same problem its still doing the same thing. if anyone could help me out or has any ideas in this matter i'd appreciate it greatly i've tried everything i can think of. thanks

Could be several things with the engine swap thats causing this.

Check and or clean the IAC if its all carboned up inside, but dont turn or push the pental, that will screw up the IAC.
Intake air control is the IAC, its on the throtle body(TB).

Could hav a fuel filter cloged, wet or damaged ignition system components.

Wrong gap on the plugs or bad ones, and the obviuos, a vacum leak at the intake manifold or in one of the vacum lines on the motor.
Since the engine was removed, this could be very likly what the trouble is.

Good Luck and I hope this helped you!