stalls when put in gear

i have a 94 z24 cavalier that runs and idles fine but when put into gear and brake is released it gives a jerk and shuts off. does anyone know what this could be? the mechanic that worked on it b4 said there was a "brake" on the trans that he unhooked and i was thinking maybe this brake somehow got pinched and is locking up the trans... please reply with any insight thanks

Check codes. If there are any, post them. Whether or not there are any, try wiggling/pulling on wires that flex when the engine is put into gear.

i have a 2004 cavalier ls, and it jus wont start, it does kinda start but theres no power, i mean i have one of those loud mufflers on 2 but when it starts it just sounds like a stock vehicle, and we changed da fuel pump, fuel filter, got another fuel pressure regulator, got n new coil and a new module 2 and it still wont start, i need help!!!! PLEASE, WHAT COULD IT BE?