What cause a knocking noise 5 to 10 minutes after first start in the morning?

First of all, I have checked several responses from you on this website and you rarely give advice except for something similar to what you posted here. Second, I checked with the Cadillac forum (same engine) and found out a service bulletin for this problem. It states the knock is caused by the engine heating up before the cadalitic (spelling ?) converter. The system is programmed to puff 3 to 5 hot blasts into the converter. It says it will sound similar to what I stated in my question.

I checked with the Cadillac forum (same engine) and found out a service bulletin for this problem. It states the knock is caused by the engine heating up before the cadalitic (spelling ?) converter. The system is programmed to puff 3 to 5 hot blasts into the converter. It says it will sound similar to what I stated in my question.