Rattle only from 4.8k-5.3k RPMs - can't diagnose

[hkovalcik]

Hi all -

- Harsh rattling/marbles in a can/similar VANOS rattle noise
- ONLY happens from 4,800 RPMs to 5,300 RPMs - I can get it to happen every time
- No loss of power when WOT through the powerband and can't hear it if I go WOT thru the range of the powerband
- If I let off the gas after WOT around high 5k RPMs and let the RPMs fall, it seems to happen/feel the worst then
- No issues other than that and never, ever does it other than in that RPM range. Thing runs great and pulls strong other than this issue

I'm thinking cam bolts, broken tabs - something with the VANOS. The only reason I posted this thread is that I could not find any other thread where someone had this issue only at these RPMs - all of the VANOS issues seem to be at the 1,500 - 3,000 RPM range.

Any help is appreciated. I do not think the whole unit is faulty, and I have not pulled the cam cover to inspect the tabs, etc. I haven't really messed with it because nothing has broken - it's been doing this ever since I bought the car about 2 months ago - I'm assuming the PO who had it for a year or two also had this issue but never did anything about it.

[dworthy]

I would start with pulling the valve cover and have a look at the tabs. Next I would look at the chain and sprockets, see if it is loose or the sprockets are very sharp.