2008 Yukon Denali XL: Rough Idle/Accel after changing spark plugs

[swathdiver]

That works or two adapters using a 1/4 ratchet and 3/8 socket.

 

[Les W]

Reid, I was wondering if your engine had AFM hardware or not, thought it was an '07 but see that it is an '08 and does not have it. The very early SUVs with the L92 had AFM hardware but was not active in the tune. It was physically removed later in the year and for 2008.

I found that no swivels work on that one and neither did going in from the wheel well with our tools. I just need to someone skinny up there with more heft and muscle than my last helper!

Hi Swathdiver, I have been following this thread as I have a 08 Yukon Denali and I have never been able to confirm if I have AFM. I bought a Range finder because they swore I have AFM. I have noticed threads reporting you can verify in DIC but I cannot find anything to support different modes. You mentioned the valley cover flat or lumpy. Would the lumpy valley cover indicate the selenoids present ? I would love to have no AFM, that would make this motor that much better.

 

[swathdiver]

Hi Swathdiver, I have been following this thread as I have a 08 Yukon Denali and I have never been able to confirm if I have AFM. I bought a Range finder because they swore I have AFM. I have noticed threads reporting you can verify in DIC but I cannot find anything to support different modes. You mentioned the valley cover flat or lumpy. Would the lumpy valley cover indicate the selenoids present ? I would love to have no AFM, that would make this motor that much better.

Your engine's RPO code is probably L92 which did not have AFM. The very earliest L92s, those made by April '06 for the 2007 MY had AFM hardware but was not active in the tune. If you did have AFM and it was active, when driving at a steady speed and the DIC set to the instant average, the screen would say "instant econ v8" or "instant econ v4" above the current mpgs.




Yes, the lumpy cover indicates AFM.

 

[Les W]

Your engine's RPO code is probably L92 which did not have AFM. The very earliest L92s, those made by April '06 for the 2007 MY had AFM hardware but was not active in the tune. If you did have AFM and it was active, when driving at a steady speed and the DIC set to the instant average, the screen would say "instant econ v8" or "instant econ v4" above the current mpgs.

View attachment 200845


Yes, the lumpy cover indicates AFM.

Well I am pretty ecstatic, my valley cover for as much as I can see is flat and my instant economy does not show anything as far as 4 or 8