LQ4 Pulling Max Timing When In PE

[alex_m]

Hi all! Been working through the tune in my 02 Silverado. This is my work truck; basic 6.0, 862 heads, Summit cam (forget which; torque cam), shorty headers, 92mm throttle body on nnbs intake, NV4500 swapped.

I have a wideband in the truck, but it is not connected to my MPVI2. I am running 93 octane and stock high timing table in both tables right now.

I am having two issues: one where the truck is pulling max timing (currently set to 8*) any time it enters power enrichment. Pulling timing out of the timing table makes no change, and I am not hearing any spark knock. Seems like nothing I do has any effect.

The second issue is that, right around the 1500 rpm mark under mid throttle I actually can hear a small amount of spark knock. AFR is stoic. I have tried adding a little fuel and removing a degree of timing in that area, no change. The odd thing about this is that if I am running just on MAF or just on VE it does not happen, but when I have both enabled it does happen. Knock sensors do not pick up on it.

I've included my most recent tune and a driving log. Any assistance would be greatly appreciated!

00196_StockHighTimingTable.hpt
00196.hpl

[STAGEUP]

Sounds like you have a bad knock sensor or bad knock sensor harness.

[alex_m]

I did a while back, and had a code. I have since changed knocks sensors and harness and the code has been gone the last 4-5k miles.

I have worked on the timing table some and the truck has been detecting knock in places, pulling out 1-2 degrees when not in power enrichment. I have since reverted to stock timing table to start fresh.

Edit: I have had the knock sensitivity turned down very slightly in the low rpms - did not have time to stop and change that today, I just stayed out of the range it was happening in. I just reverted it to stock sensitivity to see if that shows the knock that I hear.

[blindsquirrel]

It's real common for there to be something wrong that doesn't set a Pending or Current code, but still makes it default to max retard in PE. The sensors will still work detecting knock and pulling timing when there's real knock detected even with the codes set to No Error.

[alex_m]

Understood - I'll set the codes to no error and report back. Thanks!

[Alvin]

I'll bet if you scan it it will have a knock sensor code pending.

[edcmat-l1]

If you're hearing audible knock under light load I would start by doing an induction service on the vehicle to get it de-carboned. Might want to try high octane fuel if you're not already running it. If you are, try a can of octane booster. See what happens. If you don't find any results there, might try LS6 knock sensor settings. See if the helps the KR in PE. The timing is not near high enough to cause knock at WOT. It's pulling 8 degrees and you're left with 5. 13 degrees total should not be knocking unless the fuel is crap or the engine is all carboned up.

[alex_m]

I set the knock sensors to no error reported and that solved the issue pulling timing. I have begun tuning the ignition timing and the ECU is still detecting knock just fine. When I feel pleased with my results I will post back to have my tune looked over.

If you're hearing audible knock under light load I would start by doing an induction service on the vehicle to get it de-carboned. Might want to try high octane fuel if you're not already running it. If you are, try a can of octane booster. See what happens. If you don't find any results there, might try LS6 knock sensor settings. See if the helps the KR in PE. The timing is not near high enough to cause knock at WOT. It's pulling 8 degrees and you're left with 5. 13 degrees total should not be knocking unless the fuel is crap or the engine is all carboned up.

Thanks! Motor only has 15k miles on it. I am thinking bad gas was the issue - I filled up with fresh 93 yesterday morning and the knock at low RPM went away.