knocking and idle symptoms are two separate problems.
reset your idle before you run out and buy any type of sensor. When I do work on my car that requires battery disconnection, I will have a bouncy idle if I dont set the idle correctly. Simply hooking up the battery, starting the car and driving it will cause the idle to bounce like yours is doing.
The knocking could be from several sources, not just the rod bearings.
Valve lash ticking is rare.
Cam Chain tensioner ticking is the next thing up from valve lash
Timing belt tensioner failure for automatic SHO's is most common.
Rod bearing knock is not rare, but has other bad things associated with it like very low oil pressure indicated by the oil light coming on, and metal flakes in the oil.
