What did you do to your NNBS GMT900 Tahoe/Yukon Today?

[Doubeleive]

maybe it's just my brain but the engine doesn't even sound normal to me anymore, something has changed even just idling something is different and it's not a rattle or tick or anything like that it just sounds different than it has before. could be my imagination....

 

[Doubeleive]

would the specific cylinder misfires correlate with a bank noise causing knock?
kind of wouldn't make sense though because a lot of the misfire are on 2 & 7

 

[Doubeleive]

misc data, in case anything looks off

 

[gooffeyguy]

the thing is there is no reason for this to be tune related at all, I switched it 3 times including going back to what was on it before blackbear sent me any tune and no change.
something is causing this just need to figure it out.

It's that lost 10mm socket rattling around somewhere

 

[mikez71]

^^^ Could be, right?! ^^^

actual timing should be actual.I saw a -12.5 degrees timing shown at one point.
I thought max was -10, but who knows there maybe some other adders or multipliers.

Looking at MY previous normal graphs, timing tends to stay above 16degrees (warmed up),
EXCEPT during shifts, I see spikes down to -5 degrees (final advance) very briefly.
(pretty sure that is a torque management shift setting)

With the loose mount/knock retard, timing advance could stay negative.
Never dipped below -10, but would often be negative once knock retard kicked in.

My indivudal cylinder knocks were all nearly identical, despite it being close to one knock sensor. Could be the vibration just rings the whole block.
(Or I suppose the knock was so continuous it continued throughout all cylinder ignition events evenly.)
About your cylinder misfires, did they move around? I though I saw some different cylinders before it was 7 & 8. Think I read misfires are sensed by the crank speed..

 

[swathdiver]

View attachment 434938

Fuel Pump trims look good, better than mine and about the same as my pickup.

 

[swathdiver]

I'm trying to think, I think mine did something similar a few years ago. Intake gaskets or spark plug gap, can't remember.

 

[Doubeleive]

^^^ Could be, right?! ^^^

actual timing should be actual.I saw a -12.5 degrees timing shown at one point.
I thought max was -10, but who knows there maybe some other adders or multipliers.

Looking at MY previous normal graphs, timing tends to stay above 16degrees, EXCEPT during shifts, I see spikes down to -5 degrees (final advance) very briefly.
(pretty sure that is a torque management shift setting)

With the loose mount/knock retard, timing advance could stay negative.
Never dipped below -10, but would often be negative once knock retard kicked in.

My indivudal cylinder knocks were all nearly identical, despite it being close to one knock sensor. Could be the vibration just rings the whole block.
About your cylinder misfires, did they move around? I though I saw some different cylinders before it was 7 & 8. Think I read misfires are sensed by the crank speed..

they did but 2,7,8 seem to be more than others, 8 has came up alone a few times then it will show random.
just went to check to see if the motor moves in drive/reverse but doesn't appear to budge at all or very very little.
I guess when it cools off later this evening I will get under it and tap around with a mallet

 

[mikez71]

Only thing that stands out is the continuous knock for a couple sessions..?
looks like it feels normal cruising slowly? Once you roll up past 3500 rpms it retards

I don't know if this is the problem, but I bet if you take the starter out and feel it in your hands, you'll want to replace it.
Might be a good time for that maintenance..

 

[j91z28d1]

I'm trying to think, I think mine did something similar a few years ago. Intake gaskets or spark plug gap, can't remember.

I do think a vac leak is worth checking for.


I'm just guessing they did plugs and wires when they replaced the lifters?