Timing retarding -10 deg no knock

[Suburban]

I was wondering if someone would have an idea what is causing my timing to retard -10 degrees no knock when the engine is hot accelerating from a stop. If I accel very slowly it is not as noticeable but still there. The engine runs excellent when it's cold. It's a 5.3l no vvt and afm disabled. It still has the stock cam and lifters whether that is causing any issues I'm not sure. I had relocated the IAT sensor and boxed in the cold air intake filter as well as adjusted some parameters with no luck. I purchased the engine complete from someone that said it came from a 2012 Sierra but he had no paperwork so couldn't confirm it. When I had the harness built and ECM programmed I had it made for the 2012 5.3l and the stock 4L60E trans. in a 1998 Suburban. When I installed the engine harness the MAP sensor connector was the only one that didn't fit. I now believe the 5.3 is probably a 2008 truck because the MAP sensor for anything newer than 08 is different. So I made a newer sensor fit and again I'm not sure if this is an issue. I attached the tune and log of what is going on if someone could look at it and hopefully point me in the right direction that would be great.

Thank you

[5FDP]

Log knock retard and burst knock. You want to see if that is causing the timing to nose dive. There is no knock control under like 120-140 degree coolant temp so it won't yank all the timing away.

So the current MAP sensor is from a 2012 or similar year truck? I know the 2007 to 2009's run different sensors so the linear and offset settings are different.

Is fuel pressure good and around 58psi and are the injectors in this setup the size the tune says they are?

[Suburban]

The current MAP sensor is for a 2012 5.3l. I still have to check fuel press. And the injectors are stock to the engine, thats another thing I was wondering about being an issue. Is there a way to change the injector data?

[5FDP]

The MAP data is correct then.

Yes, all the injector data can be changed if they are a different size then what the tune is currently setup for.

Add those knock channels so you can see if it's knock. Check for cracked or broken sensors too and anything that could be touching the frame or causing vibrations.

[Suburban]

Here is an updated log file I just recorded with the burst knock and knock retard recorded.

[TCSS07]

you appear to be knocking pretty bad which is what is causing the timing to dive which will cause the ecm to switch to the low octane table and will blend back to the high octane table when it subsides ... id suggest lowering the timing like 3-5 degrees in those areas to start out and re log ... i don't see any misfires counting up so that's good

[5FDP]

It seems to be a few things for sure. With all the knock it's seeing it's mainly going to be using the low octane timing curve. If you logged the knock learn factor it will show you a number between 0 and 1. The higher the number the more it's going to use the low octane table and blend the timing between the two tables.

If you look at your low octane timing curve you have tons of negative numbers in the low rpm range and medium to high cylinder airmass. You should not let the timing drop that low. To stop it from going so low you will want to raise the timing up a lot. Have it stop somewhere around 8-10 degrees as a test. Make it blend into the rest of the timing at around 2600rpm where it's at 8-10 degrees. I think you'll see what I'm getting at. I want to see if doing that helps with the timing going so low when you get on the gas.

Burst knock is also removing timing at random as that is a predicted knock table. It can happen on throttle transitions. I'd honestly just disable that so it stops doing that, it's rather annoying to deal with. Under Engine > Spark > Retard > Burst Knock > Base vs Cylair delta, zero out that whole table.

Again verify fuel pressure and that nothing is rubbing the frame to cause random knock to be picked up by the computer.

I saw some random misfires throughout but they stopped at like 2 per cylinder and were completely random.

[Suburban]

I made some adjustments to the low octane table and it's a lot better. It still has some KR but not like it did before.

[TCSS07]

you want to make the adjustments to the high octane spark chart ... the low octane chart is for ref when it is knocking for safety but is not used for the primary spark look up but by making the high and low charts more similar it will lessen the spark change fluctuation

[5FDP]

But if you notice, the timing changes are not as great now because he adjusted the low octane timing curve. The reason being is because he had so much knock that the only table it was using was the low octane timing curve but if he was logging the knock learn factor it would show that it's taking everything from the low table.

Because he took away the computers ability to ask for such low numbers is why it's not going to -10 degrees right now. It still drops low because there is some knock but not neally as low.

Though you are still right, the high octane table is what it uses first but if there is knock the knock learn factor will now make it blend between the two tables depending on how large/much the KLF is.

[TCSS07]

true which is why i stated by making the charts ho and lo more similar it would lessen the spark fluctuation but it also wouldn't have to fluctuate so much if he lessened the ho spark numbers to get rid of the knock all together so it wouldn't even ref the lo chart

[Suburban]

I've made a few changes with the low/high octane tables and still get KR. But I noticed when I accel from a stop that is when the KR happens, and while theres a KR reading on the screen if I release and apply the accel pedal it drops to 0 and usually doesn't return until the next time I stop. There are very low KR's in neutral with light revs. I noticed the crank pulley has a slight wobble to it if maybe this causes issues? And do the injectors have to be recalibrated?

[TCSS07]

well the balancer wobbling is not good and should get replaced asap - dont want that falling off and it could be possible i suppose if the balancer is going bad to have the engine pick up harmonics thinking its knock or possibly screwing with the crank sensor but thats not causing the issue. you dont hear pinging or anything do you? also no dtc's?
are the injectors from a 5.3l also?

heres a stock 2012 silverado 5.3l file to verify injector data if so
Attachment 81120

[Suburban]

No pinging, no dtc's and yes the injectors are original to the engine which I believe is a 2008 but the ecm is programmed for a 2011

[TCSS07]

i dont have a 08 5.3l file so id try the look around for one or check the tune repository for one to verify some of the settings because the vehicle is commanding lower spark advance during acceleration even when its not knocking because of the knock that has happened

[Suburban]

What does the spark adder do exactly? Im very new to tuning and knowing exactly what to change.

[TCSS07]

like ect, iat, alcohol adder ... they all add or subtract timing based off certain conditions like temperature and cylinder air mass, etc. if they apply to your set up and so forth ... but first id move the ho spark chart to the lo spark chart to make the timing the same to get the spark more in line but that knocking needs fixing so if you copy the ho to lo you need lower the timing more in the middle by at least 5 degrees since some cells reached 10 degrees knock and re evaluate

[TCSS07]

re looking at the last log you posted and 5FDP stated this above also about the lo spark chart ... but your car is getting stuck in lo because of the high knock and wont recover ... meaning it never returns back to the ho spark chart

in the log - at 2:56 minutes its commanding 5 degrees advance @ .48 airmass @ 35-36 tps% @ 1600rpm @ 30mph which on the low octane chart is 7 degrees advance and then subtract 2 degrees because of iat spark adder table @ 88 degrees which would net the 5 degrees advance shown on the scanner

[Suburban]

Ok so I copied the tune for the 2012 Silverado which is the same as what I had and it caused the same issue. So I reinstalled the previous tune and made the hi octane and low octane tables the same as a test. The KR is still being read but it does not retard timing like it used to. Could it be possible the knock sensors are picking up noise from the headers? And can the sensitivity of the knock sensors be adjusted?

[TCSS07]

could be so maybe also check the torque if there loose or over tightened make sure the wires arent touching the headers or anything or perhaps maybe put new ones on if there old couldn't hurt ... they may cause issues but yes you can under knock sensors - knock sensor level - you can raise the values to decrease the sensitivity but you don't want to raise them to far and inhibit them from doing there job - start slow - initial move up to 150 and min move to 75 to start and see if it makes it any better but after checking everything like the sensors for proper torque and by you changing the spark values to the 2012 file then the knock its going to be real - what octane are you running? maybe the vehicle needs more if your using 87 - also you need pe to come in sooner than 5k set the delay to around 3k and drop that tps enable to around 30-40% to have it enable around 60% - dont need to be running lean up top