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

[Doubeleive]

@Doubeleive So your fuel pressure is running at 55 psi? Is that commanded as well? Either way, I've never seen with any of mine, they always run 43.5 psi at idle and at WOT.

What is your Fuel Pump's LT Trim? I believe this is way to gauge the pump's health.

it only did that one time, I'll have to go out and see what lt trim is I think it is fine though the pump is only 1yr old had it replaced by the dealer last year

 

[Doubeleive]

@Doubeleive So your fuel pressure is running at 55 psi? Is that commanded as well? Either way, I've never seen with any of mine, they always run 43.5 psi at idle and at WOT.

What is your Fuel Pump's LT Trim? I believe this is way to gauge the pump's health.

 

[Doubeleive]

averages from a 9 minute run, I'll try and video the playback or if anyone has any idea how to decipher a efi file I can send it via google drive or something

 

[j91z28d1]

averages from a 9 minute run, I'll try and video the playback or if anyone has any idea how to decipher a efi file I can send it via google drive or something
View attachment 434939

not that I think it's the fuel pump, but do you have a chart like this that shows fuel pump trims range and adv? I have no clue if 1.4 is good or bad.

 

[Doubeleive]

looks like some knock is kicking in around 3500 rpm and up under a load, uploading a video I guess efi plays it back at like 1/10 the speed

 

[Doubeleive]

 

[Doubeleive]

I have no idea what is normal for engine knock, here is what mine looks like

 

[mikez71]

saw a max of 13.4 deg knock retard in your first photo.
video shows you staying in knock retard.. I know what it feels like!

should be 0 knock for the most part..

check motor mounts, starter, anything close to the knock sensors that could be rattling..

 

[Doubeleive]

saw a max of 13.4 deg knock retard in your first photo averages..!

ya, is that bad? I don't know anything about knock or how much is normal or bad.

 

[j91z28d1]

unless it's been changed max knock retard is 10deg and I didn't see it hit that so while it would be nice to have zero, seems like something the ecm can get on top of, or it would be maxed out retard..

I still am not clear even own truck if the timing shown is the actual timing with the knock retard removed or if that's like the base timing and you gotta remove the say 5-7deg in your head.


either way I don't believe that's why it's running bad but hopefully black bear will know if they need to reduce tuning a bit or let the ecm do its thing

 

[j91z28d1]

saw a max of 13.4 deg knock retard in your first photo.
video shows you staying in knock retard.. I know what it feels like!

should be 0 knock for the most part..

is that what that means? I watched the video and didn't see that much.


in my hybrid tune 10deg is max. do you know what the max the normal trucks let your retard?

 

[Doubeleive]

unless it's been changed max knock retard is 10deg and I didn't see it hit that so while it would be nice to have zero, seems like something the ecm can get on top of, or it would be maxed out retard..

I still am not clear even own truck if the timing shown is the actual timing with the knock retard removed or if that's like the base timing and you gotta remove the say 5-7deg in your head.


either way I don't believe that's why it's running bad but hopefully black bear will know if they need to reduce tuning a bit or let the ecm do its thing

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.

 

[Doubeleive]

is that what that means? I watched the video and didn't see that much.


in my hybrid tune 10deg is max. do you know what the max the normal trucks let your retard?

I only recorded a couple minutes of the 9 minute run just to show what it is doing

 

[mikez71]

max final timing maybe -10, but you can still have more retard.
So if his timing should have been 10 degrees at that moment, it would then be -3.4.
It's a lot of degrees, this is exactly what I felt with loose motor mount bolts.

 

[Doubeleive]

saw a max of 13.4 deg knock retard in your first photo.
video shows you staying in knock retard.. I know what it feels like!

should be 0 knock for the most part..

check motor mounts, starter, anything close to the knock sensors that could be rattling..

i'll jack it up later and see if I can find anything, motor mounts were both replaced with the hummer mounts which should be ok but I will take a look

 

[mikez71]

Original starter?

Regarding motor mount bolts,
I heard no noises, and only noticed one bolt was missing.
Put wrench on the other 3, all loose!
I must have forgotten.. was extremely tired/weak.. or. I'm not saying it was aliens.. but.

 

[j91z28d1]

yeah, I agree it's not you're main issue.

 

[89Suburban]

Man what a PITA Wes! Sorry man! Wish i could be helpful.

 

[Doubeleive]

Original starter?

yes, it's never even blinked at me but I can bang on it when I jack it up and see

 

[j91z28d1]

max final timing maybe -10, but you can still have more retard.
So if his timing should have been 10 degrees at that moment, it would then be -3.4.
It's a lot of degrees, this is exactly what I felt with loose motor mount bolts.

I wonder where it's getting it extra timing amount to pull over max comes from.



I have wondered if the timing value shown is the actual at plug timing, or like you say, you gotta do the math and subtract the retard.