Originally Posted by 2010BHDodge
I've seen two other 09 hemis do this. A dealer told me it was "piston slap" on startup but that doesn't sound right. I would suspect more to do with lubrication - either the light oil or if there is the check valve problem as mentioned in earlier posts.
I had what I thought was piston slap on a Silverado once... BUT, I was able to fix it
Long story short, a knock sensor (and the wiring to the sensor) under the intake manifold was going out, and it pulled the timing out of kelter,,,
The knock would go away a few seconds after start up.
It knocked (occaisionaly) for months,,, Finally, the sensor 'died' and activated the MIL.
Read code, replaced sensor, knock gone.