Hi everyone, I have an '04 Alero with the 2.2L Ecotec engine. My stepson blew up the original motor so we went to a local wrecking yard and pulled a long block to replace it. Everything seemed ok with the engine so I dropped it into the car and discovered a misfire. It set the code P0302. After troubleshooting and finally pulling the valve cover to look there I discovered one of the little roller rockers laying on it's side. Cylinder 2 intake side. As seen in the pic below. Nothing looks broken or scarred so I'm wondering if anyone out there has any idea on what may have caused this? Also, I can put the rocker back in place but it's so loose, it'll just fall off again when the engine rotates. Would replacing the cam and this rocker fix the problem? Thanks in advance.
UPDATE: After checking more, turns out the valve was partially stuck open allowing the slack. Going to pull cams and work all valves with some marvel mystery oil to help them out.