first the good news -- yesterday dealer told me the warranty company finally agreed to pay for a new engine. yay!
to your question -- it wasn't like a dieseling sound so much and it was much louder. It sounded like when i had bad lifters on an old car and they all had to get replaced. For the QX, it would come on cold starts (say below 40 degrees and car had been sitting awhile), and last for 1-5 minutes, varying with the engine speed. It seemed to be progressing quickly over the 2 or so weeks i had the noise, but the car drove fine (other than the intermittent stuttering the car has always had that no one has been able to fix...hopefully the new engine fixes that...i also wonder if that is what caused this problem in the first place).
The DI does make a sound that you could say is a dieseling sort of sound, yeah. But it is quieter than what i had.
Funny part is they still don't actually know what the problem is. They just know it is bad/eventually fatal.