2000 ford windstar clicking during accel.

our van is making a clicking noise, almost sounds like it is coming from the lifters, underneath the valve cover... during normal idle it can barely be heard but when the van is accelerated it is more noticeable, clicking becomes a clank. It does not always make the noise, at least we don't always hear it.. wondering if anyone has ran into this issue, if so, what was the resolve.

art

Is it during acceleration?, mine does it too. Sounds like in the old days when you used the cheaper gas and got the spark knock. I used a higher octane gas and it seemed to help. But I will ask a mechanic at work and will post a reply.