My F23 is making a cluncking noise from the #1 cylinder. The noise isn't enought to scare me but its fairly pronounced when at idle.

My roomate said it might be an exhaust leak at the header so I took off the cover for the first time in the accords life and I noticed the furthermost right bolt on the header was missing. It was the bolt and stud that were gone!!!! I nor anyone has ever taken that manifold cover off so I can't see a reason for it missing. We felt around with the engine running and coulldn't feel any exhaust leaking out so I think I can eliminate this as a cause for the ugly sound.


Pls help me diagnose the problem. I'm going to adjust my valves soon, but I don't think they are making the sound. I was also told it could be a worn out rod at the piston.