160k 09 Yukon XL, replaced fuel pump, pulled injs to inspect and then put it all back. Truck fired up just fine but, a couple days later I logged it and noticed KR in a bunch of places.
I logged it this morning on the way to work.
If anyone can spare the time please, take a look at the tune and log and let me know if it's something obvious I am missing or if my truck is now knocking like a punk???
confused, why so much KR stock tables.hpl
back to stock timing...again.hpt
Are you really running 13% E content?
I see it's still on the factory virtual sensor, they are completely inaccurate and seen them cause several problems. I disable the virtual sensor and keep the stoich at 14.68 in my truck.
Otherwise it looks fine for a factory tune on cheap 87 octane.
2016 Silverado CCSB 5.3/6L80e, not as slow but still heavy.
If you don't post your tune and logs when you have questions you aren't helping yourself.
I was wondering about that, noticed it when I saw commanded 13.98. I'll disable and set my stoich flat across the table at 14.68.
Are you saying that a normal tune knocks that much? I run Shell 91, really surprised it's knocking that much.
Also, where is the disable for the virtual sensor?
NM, found Flex Fuel Disable and turned it all off.
Last edited by mercrising; 06-16-2017 at 03:00 PM.
Figured it was on regular pump 87, most all stock GEN 4 trucks that I've seen knock like that on factory tunes and 87 octane. Maybe try fueling up a different place and see if anything changes after you change the flex fuel setting.
Engine > fuel > open/closed loop > flex fuel. Then just set it to disabled.
2016 Silverado CCSB 5.3/6L80e, not as slow but still heavy.
If you don't post your tune and logs when you have questions you aren't helping yourself.
I just bought a 2007 Yukon XL with 175k miles and am seeing pretty much identical KR as you. Previous owner admitted that oil consumption was high which didn't surprise me as I had done some reading about the DOD/AFM oil consumption problems.
I have turned off DOD and have done some work lowering the low octane spark advance table to reduce/eliminate the KR. I'm still very curious how much of the knock is due to carbon buildup, oil burning, and/or an aggressive stock timing table. The timing table is pretty mild compared to what I've seen in a lot of tunes so I can't help but think it's related to the oil consumption.
I checked my plugs and they had a lot of carbon buildup and had pretty large gaps .050+. I cleaned them up as best I could and regapped them to .040 but haven't had a chance to do any logging since. I also cleaned the MAF.
Regardless of the KR and oil consumption the yukon runs well and achieved 17.5 mpg with a load of people on a 300 mile trip mixed highway/freeway with the AC running. If I can improve on that I'll be very happy.
My plan, not necessarily in this order:
* clean the piston crowns/combustion chambers using gm's cleaning method (http://amzn.to/2ufk7xx)
* Disable flex fuel and set the 0-12% stoich cells to 14.13 to match the 10% ethanol gas we have in OR
* Install new o2 sensors and spark plugs
* tune the maf
* tune the VVE
* tune the low octane spark table on 87
* tune the high octane spark table on 92
* i might try to adjust the per-cylinder injector gains to richen up the knock prone cylinders slightly to see if I can give it a bit more timing
EDIT:
Forgot to mention my motor is the vin 3 LC9 with the aluminum block.
Cool deal, I was just poking at the idea of running the stoich at that rate too, we have about 10% Eth here in CO for fuel too.
Like 5FDP said, most all GEN4s show that much KR. Everybody agrees that if you remove ignition to the point that you no longer see KR....worse fuel economy and no power. GM just sets them up that way. The sensors are set quite sensitive to the point that they are picking up a hint of detonation and doing something about it way before something bad happens. I can add that cold air intakes help and tuning VVE accurately helps quite a lot.
Good to know, appreciate the input.
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