My 2006 3.5L with 218K miles is in constant knock. There are no codes and the MIL light is off. There is a noticeable misfire between 1500 and 2000 rpms, noticeable performance loss. The knock is present in park revving from idle and noticeable under load at any speed. Starts easy, runs great outside of the mentioned rpm range. If accelerated from a stop, runs right up through max rpm and shifts well.

Spark plugs were recently changed and all but #4 were eroded, #6 was the worst. Also, I changed the knock sensor, no change, knock still present.

Any insight would be greatly appreciated!

 

Rod knock or cracked flex plate maybe.....

 

If there is a bearing or wrist pin bad, I can't hear it. And, I've heard the noise from cracked flex plated (sounds like a bad wrap noise) but again, nothing noticeable.