I have a 1997 Honda Accord EX. It has about 160,000 miles. The check engine light came on and I brought it to my mechanic who scanned and said it was the EGR valve. However, upon inspection, he discovered there was nothing wrong with the valve. He cleaned it and it works properly. He replaced the gas filter which was in need of replacing, and put a fuel injection cleaner in the car but the check engine light remains on. He checked with two other experienced mechanics and none of them could figure out what the problem is. They "checked everything". The car rides rough and there is an engine noise that I don't like - it's not loud but it bothers me. It seems to "tick" just before shifting to the next gear.