My '02 has 116k miles. I have a hollow knocking sound on cold start, I knew I needed to adjust the valves anyway so I did it a few weeks ago. The knocking is still there and I'm pretty sure it isn't valve noise. It does diminish when the van warms up. My next thought was piston slap. After doing some searching on the forum, I'm leaning towards this being the issue. So, who else has piston slap? If you do have it, is my description of a hollow knocking sound accurate?