Hi everyone. I am a new poster but i have been visiting this forum for months since I picked up my 06 QC 5.7. I have exhaustively searched the forum and I think i may have found my answer but I am not certain.
background 34k miles, k&n 1533, m1 5-20

when i cruise from just about 1400-2100 rpm i get a laboring and somewhat clunky sound from the engine, like it needs more throttle, and then if i lift off of the gas, I get a somewhat of a "backfire" sound, but almost like a sneeze or rush of air "dzoooo" if i where to phonetically spell it to have you hear it in your head. even if i keep constant throttle it will sometimes do this. if i give it some juice it is back to normal.
if i watch the tachometer, i see about a 50-100rpm sudden drop when it "sneezes and acts like normal again. I don't know if this constitutes a ping, but any help is greatly appreciated.
Thanks a lot,

 

try running with overdrive off it sounds like the overdrive at to low a speed, you are probably around 40-45 mph when it does it and it wont at 55 or higher

 

still made the noise- OD off under 35 and OD on at 75

 

any other ideas?

 

Take your truck to Autozone and get it scanned for any P-codes. If there is anything wrong, a code will "usually" be thrown, and it will help zero in on what may be causing the problem

 

mds is cutting in. the sound will change and the rpm goes up a bit while in 4 cyl mode. if you step on the gas it goes to 8 cyl.

 

Ok so i took some (admittadely bad) videos here they are, #1 occurs around the 14 second mark and #2 around 45 seconds
http://www.youtube.com/watch?v=u2YL95Mx34k
http://www.youtube.com/watch?v=1p-t9ieYn9c

Thanks

 

I went to advance auto and they said with no cel they couldnt pull any codes, i did the ignition cycle and only "done" came up, no codes. this is getting very frustrating ...

 

Sounds like the MDS kicking in and out. Hard to tell, you don't keep the throttle steady.