PrecisionH23a

Hey guys, a buddy of mine has a 94 hatch with a 1st gen b16a motor. Before taking the motor out, it ran fine. He did a few things to it and since they just put it in again when you crank it it will start for a second then shut off. If you give it a good amount of gas for say 5seconds it will keep the motor alive and then magically stay idle and it wont die. Once its running, it drives fine without any hesitations or anything. Any suggestions as to what to check? Thanks.