I have a 1999 Acura TL with 200K miles on it. It always had a tap that sounded like a bad valve, but recently it started tapping making a sound like an overhead cam hitting metal as the car accelerated. I had it checked out at the acura dealership and it revealed a broken ignition coil which when they tried to replace it with a test coil the spark plug would not tighten up. When the engine cranks without it there is a loud engine noise. Question what can be done beside replacing the engine?

Most auto parts places (autozone, advance, ect) sell a spark plug rethreading kit, with a steel insert. Basically you enlarge the hole, then rethread it, then install a steel insert. This kit will work, I have personally used it with great success. My own comments are this though: when you are using the cutting/retheading tool pack it with wheel bearing grease to help catch the shavings. Before you install the insert breifly start the car and let it blow any shavings out of the cylinder. Then when you install the insert use the highest grade of loc-tite they have. My kit said to use RTV but I prefer loc-tite. Follow the instructions to the tee and give the loc-tite 24 hours to cure before starting the engine and you should be fine! Good luck!