One problem related to engine clicking and tapping noises has been reported for the 2007 Saturn ION. The most recently reported issues are listed below.
As I was heading home from work, about 3/4 of the way home on the freeway there was a loud "bang" and a jolt in the car that was immediately followed by a high pitch "squealing" sound. I got off at the nearest exit and took other roads home at approximately 40 mph. The squealing continued the entire way home, but would stop when I had to stop at lights. As I was turning onto my street, a battery light error came on the dashboard and my car simply shut off and would not start. I was towed home and did not do anything to the car for 3 days. On the 3rd day I attempted to jump the car with another car and was able to get the engine to start, but immediately a different check engine light came on and a different loud sound was coming from the engine. The new sound was not the original squealing. After opening the hood, I found a large metal "chunk" was lying on top of the engine cover and a hole had been made from where it came out of the engine bay from. The only thing I can gather is that it may have been caused by a timing chain failure, because the only thing preceding the incident was a very faint clicking sound coming from somewhere beneath the hood.