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

[tuckerrnr1]

It's the home made fireworks I'm worried about

Many years ago, we always went to a family friends house on July 4th. Large piece of property, lots of small lakes and islands from years of shellrock quarrying. We always had several gross of whistling moon rocket bottle rockets and used the islands for bases for bottle rocket wars. Some years we broke out the canoes to include naval assets to the carnage. One of the men was a licensed pyrotechnician and made homemade ordnance. One year he made a candy mortar for the kids. Picture a five gallon bucket with a 4" tube surrounded with concrete. He used a cut 2 liter bottle to house the candy. First attempt launched the candy to God and the astronauts, the kids were like "WTF dude?". Second time he inverted the housing but while it worked, it also burned all the wrappers to the candy, once again the kids, "WTF dude?". Third time was the charm. 3,2,1 we have lift off and candy rained down from the heavens. Good times.

 

[j91z28d1]

I thought the rear sensors just watched the cats for malfunction and reported if any seen. Didn't think they affected engine operation in any way ???? But....am not positive about this.
Good Luck with it !

that's how I understand it too. they just look at the frequency of movement vs the front along with when dfco kicks in, how long before the lean spike hits. uses that for cats.

if you disable the error check, which is all hp tuners is doing when you turn off o2's, the data is still there, just ecm isn't reporting the errors from lack of cars. the engine still runs normally. I have never failed the error reporting on the front o2's. I wonder what it does. to keep it from closed loop you always move the closed loop enable temp to 255deg.


I got nothing, could be so many things.

 

[j91z28d1]

changed oil today.. about 3500 miles on it.

first change since I tried the pensoil ultra. all Mobil 1 before that. cut up the fram endurance filter that seems to be testing well these days.

was noticeablely more dirt in the filter this time. in the folds and in the bottom of the can. oil was also much backer than usual for only 3k on it. still felt like good oil thou between your fingers. Definitely didn't feel thinned out.

honestly not sure if it cleaned out some sludge in the engine or just got dirty faster. I looked around with a bore scope when I first got it and from I've been able to see the engine looked spotless inside. not even the red tint engines get but that just looking at the top of the head thru the valve cover, under the vlom when I had it off, even the oil sensor screen looked original and mostly clean. then peeking in the drain plug. I guess there could be some hidden crude in the pan cavities and stuff.


huh. well I just put the last 5qt of pensoil in it that I got for free, I guess I'll see how it looks again in a few months.

 

[Tonyrodz]

that's how I understand it too. they just look at the frequency of movement vs the front along with when dfco kicks in, how long before the lean spike hits. uses that for cats.

if you disable the error check, which is all hp tuners is doing when you turn off o2's, the data is still there, just ecm isn't reporting the errors from lack of cars. the engine still runs normally. I have never failed the error reporting on the front o2's. I wonder what it does. to keep it from closed loop you always move the closed loop enable temp to 255deg.


I got nothing, could be so many things.

Wouldn't running in closed loop constantly cause it to run rich?

 

[j91z28d1]

catch can after 3k.

kinda wild.

 

[Tonyrodz]

catch can after 3k.

kinda wild.

Seems really runny. Did it smell like gas?

 

[j91z28d1]

Wouldn't running in closed loop constantly cause it to run rich?

you keep it from running in closed loop so you can turn the ve table and maf table without the ecm trims adjusting stuff.

 

[j91z28d1]

Seems really runny. Did it smell like gas?

.
nope not at all. it felt like nice fresh oil just black. smelled like normal used motor oil.

 

[Doubeleive]

Been doing some testing replaced the rear 02 sensors and swapped in a known good maf, misfires increased???? Did a crank relearn misfires decreased and now I just get a couple on 5 & 7 which is the noisy side, swapped coil 7&1 no change, checked fuel pressure prestart is normal around 55 running it's around 43 but drops and increases 30-50 if I rev it fast. Seems like it should stay pretty stable but not sure.
And what's strange to me is after I shut if off fuel pressure increases (slowly) up to about 82 and after a few minutes it has dropped about 5 psi so it's sitting on around 77 now is that normal?

 

[j91z28d1]

I know its different but I think we have the same fuel pump module? mine the fuel pressure spikes like that any time the truck shuts off. I found it odd too, especially since it stops and starts non stop, you'd think 70+ psi would mess with the starting fuel.


if I remember right you have a tech 2? under fuel can you watch the target fuel pressure and actual psi and compare to your gauge?

since these aren't old school vacuum biased regulators, I honestly don't know what it should do when you Rev it quickly. I would think increase as that's what older return systems do, not decrease but since it's a pwm dead head setup. maybe there's a lag in the pwm before it can ramp up speed to match demand from a big pump shot? Hopefully you can see something useful with the requested fuel pressure.

if you can tape that gauge to the windshield and go for a drive a quick wot pull will tell you of the pump can keep up. I've done that a lot