Well I was hoping somebody hassome advise. I purchased an 02 STS about a year ago. It now has 90,000 miles and drives great and runs well except for this very bothering lifter noise or valve tap. I'm not really sure what it is. It's been getting progressively worse.I first noticed it during this past winter during cold dry starts. Now it does it at every start especially on a bad incline. Recently I've been noticing the noisebouncing off of a fence or a wall or even traffic. It is very annoying and also nerve racking beacause I do not want to do damage to my motor. Any advise or input would be greatly appreciated.