Question about sound and cylinder deactivation

[rwinsouthla]

Hoping someone can help me with a "sound" my 2008 Yukon is making. I'll try to be both brief and detailed. Started out with a lope at idle and reduced fuel mileage. I got on here and decided it may be the TB so I cleaned it. No luck. Then shortly after that, this sound started, which kinda sounds like a toad frog when the vehicle is between 15-20 mph decelerating and at accelerating. I then changed the spark plugs (truck has 150K, and I know that's probably a little too late, but IIWII). The lope at idle is gone...chalk that up to the spark plugs, but the toad frog sound is still there and the CEL is on. I don't have a code reader but will head to Oreilly this weekend to get it run. I've noticed that the noise happens loudest from 20 mph down to 15 when the cylinder deactivation goes from V4 up to V8 on the deceleration. It also sounds again, slightly, when accelerating but not as loudly and goes away at about 15 mph.

Sooooo, what thoughts come to your minds? What could it be?

Thanks in advance,

Ray W in South Louisiana

 

[AZSCTACO]

Have the AFM deactivated and that sound will go away. Let us know what the CEL code is after you get it