One problem related to loud engine noise has been reported for the 2003 Ford Focus. The most recently reported issues are listed below. Please also check out the statistics and reliability analysis of the 2003 Ford Focus based on all problems reported for the 2003 Focus.
The piston shattered at 109,000 miles. After doing some research, I have found many more complaints of the same thing. Come to find out that there is a design flaw in the engine when it comes to the valve seat. This happened in the #3 cylinder. The walls of the cylinder wall is so scored from the damage that it will require a new engine to fix the problem. When this happened, I was in a parking lot after shopping. I turned the key and it would not start. It also made a terrible noise. Before that, it was running fine. I had no trouble with my car except having to change an alternator. That's it. I changed the oil every 3,000 miles. I bought the car used at 90,000 miles. It was from a friend who is obsessed about keeping cars maintained. He would get a tune up, serviced, and change the oil when it was time. The car was well maintained by him. I found out there was a design flaw in the engine. But yet, there is no recall to fix the flaw. And when calling Ford, they say that there is no recall and has no intent at opening one for the faulty engine.