Shakes or Wobbles problem
1997 Dodge Intrepid 6 cyl Front Wheel Drive Automatic 310000 miles

My '97 Intrepid 3.3L V6 has well over 300,000 miles and seemed to run pretty good. Only a little bit of lifter tick at the front pass. side of the motor.
A few months back I changed out the water pump, and ran the motor for 30-45min to seat the pump. All ran good, better than before.
I Let it sit for 5 or 6 days untill I needed to use it, but when I started it up it sounded like a monkey with a hammer was in the block. And it shakes and shimmies, like an old pick-up, at stop lights while in drive. Idle is fine and steady while in park. Runs with the oil light on, level is fine.
Tick/knock is coming from the rear side of the motor, cant tell if its on the driver side, middle, or passenger.
Ive been told by a bunch of ppl that I threw a rod. But can that happen if the car sat at Idle? And if I did throw a rod, wouldnt the engine stop dead?
I have heard that on the 3.3L motors, instead of throwing a rod they break a clip, of some sort, on the lifter.
Any help would be very helpfull.