2011 CTS coupe engine or injection pump knocking

2011 CTS Coupe Spun Rod Bearing 1600 Miles

Hi - I have a CTS coupe with the 3.6L VVT DI engine with 1600 miles. When we first picked up the car in December, you could hear knocking in cold weather at idle. It took a couple of trips to the dealer, but they did find a fuel line that wasn't fully seated in a clip. After the fix, the knocking noise was far less noticeable, but my wife still heard it on occasion. Unfortunately he dealer was unable to reproduce the noise and my wife just decided to turn up the radio.

Last weekend, I was driving to Atlantic City for the Strictly Corvettes show (at interstate highway speeds) and I hear major knocking noise. I pulled over and called Onstar as I thought the engine threw a rod. Onstar ran a diagnostic and found no problems and indeed oil pressure, water temp was fine. I decide to turn around and limp home. I leave the car at the dealership, but I made a video (with sound obviously) of the engine knocking loudly at idle.

Monday morning, I go to the dealership, and the head of the service department, one of their mechanics and I start the car. At first the guys thought that indeed the engine threw a rod, it was knocking so loudly, but after listening more closely, the mechanic thought that it might be the injection pump.

Has anyone experienced a similar issue? What do you think that I ought to do if there is internal engine damage? Thanks for your input.