I've got an 85 Z28 305 TPI. Its an automatic. Car has been jerking at low rpms it does it with my foot barely on the throttle, I give it more gas and it seems to go away. Very noticeable when the car is cold, not so noticeable when it is warmed up. The jerking is pretty aggressive when the engine is still cold.

Immedietely at start up, the check engine light comes on and I get a code 42. I don't know what that is?? I don't know if that has anything to do with the bucking/jerking either.

Anyone have any idea what could be going on? thanks..