85 supra knocking 5m-ge engine

My supra just started knocking and i checked the crank assembly(rods etc.) I also checked both cams also. I removed coil wire and turned engine over and the noise is gone. I then removed all spark plugs and motor spins with no problem and no noise of a knock at all also. The knock sounds like a lose marble bouncing around inside motor when its all together and idling. I rebuilt motors before but i dont want to tear it done if its something real easy thats on a supra that causes this to happen. Any input would be great.
Thanks everyone.