So what went wrong?

I bought my 02 Bonneville SSEI in July of 08. she had 73k miles on it. right after i purchased i needed to replace the LIM (common problem). I also had the Cat replaced it was bad before i purchased the car. All was fine until a few days ago when the idle started going up and down slightly and would stall, in gear when stopped. at the same time a heard a knock under acceleration. I drove about 10 miles to the Pontiac Dealer. There diagnosis was i have a ROD KNOCK. I picked up from dealer, driving to a Mechanic for a 2nd opinion and the ROD let go.

I know these cars have there problems. I can can accept that... But...... Throwing a Connecting Rod at 75k Miles?????

I suspect the car was abused before i purchased and perhaps had a a rod knock and someone dropped the pan and threw a bearing in just to get rid of it.

PS... I never ran it low on oil. The oil had been changed just before i purchased. i have only put 2000 miles on this car since i bought it

I can't say I have heard of any engines throwing a rod under normal driving. Anything can happen I guess, but that'* not a common problem in these engines. LIM gasket yes, head gaskets and rods, not so much. Can you tell if any work was done before you bought the car?

The car seemed to be completely stock an unmolested.
I had it towed to the repair shop today. i'm gonna ask him to see if there are any signs that the oil pan had been removed previously