| Duane,
I bought a used '01 a couple years back and went through almost the exact same head scratchin' & worring about a mysterious knocking noise, sounds like similar to what you are hearing. I had the same whitish smoke puff when I stomp on it, noise louder then quiet for no reason. It drove me crazy. I tried fuel additives, changed filters, no luck. This one had injectors replaced in 2005, so they were only a year or so old, but it sounded like something was bad wrong.
Then about 35,000 miles later I did loose an injector & there was no mistaking it. While it was torn down I had the mechanic do a compression test on all eight cyliders- which were all fine. So I now know that the knocking was not in the motor.
Anyway, the new injector went in, they checked the balance & flow for all of them, everything is in spec. On my way home from the shop with my new injector - yup, you guessed it, there is a knocking sound.
So, my advice is don't stress yourself out worrying about the noise. You've checked the things that are reasonable suspects and they are fine. GM won't do your injectors without the proper codes turning up, but I would be curious to know if you still have your stock set in there or not?
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'01 2500HD Duramax LB7, Xtra cab - short box
w/ 8' Blizzard Plow, otherwise bone stock |