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

[Doubeleive]

I guess I'll presume the rise is due to heat and being a closed system no restart issues at all anytime

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

I'm think I'm looking at bank 1 lifters at minimum going to call the dealer in the morning and see what they would charge me generally they are pretty fair with me since I have been going there for 30 years the service manager has historically been more than fair with me. But if the cam is fkd I don't know. I think it needs a deeper look I reset the ecm, relearned the crank, maf, 02 sensors, swapped coils. I don't have the time to tear it down and with my luck bolts will break and that's a headache I don't want to deal with.

 

[gooffeyguy]

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?
View attachment 431023

At 120+ mph does it really matter? Lol

How many miles on that engine?

 

[Doubeleive]

At 120+ mph does it really matter? Lol

How many miles on that engine?

ya i'm sure my driving habits have had a impact, this engine has around 90-95k on it I would have to look at the paperwork.

 

[j91z28d1]

I guess I'll presume the rise is due to heat and being a closed system no restart issues at all anytime

I'm think I'm looking at bank 1 lifters at minimum going to call the dealer in the morning and see what they would charge me generally they are pretty fair with me since I have been going there for 30 years the service manager has historically been more than fair with me. But if the cam is fkd I don't know. I think it needs a deeper look I reset the ecm, relearned the crank, maf, 02 sensors, swapped coils. I don't have the time to tear it down and with my luck bolts will break and that's a headache I don't want to deal with.

I think that makes sense. Just heat soak.


of you tired to plugs? maybe toss a set of cheap non all these new fancy metals plugs as a test?

I found a spark plug loose once that caused a miss fire on the scanner but felt smooth. also something about these new plugs not needing anti-seize? and it can keep from having good ground contact.

just a thought. I forget, is this a deleted engine?

 

[Doubeleive]

I think that makes sense. Just heat soak.


of you tired to plugs? maybe toss a set of cheap non all these new fancy metals plugs as a test?

I found a spark plug loose once that caused a miss fire on the scanner but felt smooth. also something about these new plugs not needing anti-seize? and it can keep from having good ground contact.

just a thought. I forget, is this a deleted engine?

not deleted has been turned off though, I don't think it is the plugs or wires they have around 50k on them and the misfires that were happening on basically every cyl cleared up to to bank 1 only after the crank relearn. I can hear it making some noise on bank 1 more pronounced at about 1100rpm which is when the misfires start, should have had addressed it 6 months ago but the noise was pretty light and intermittent
at idle there are no misfires and at higher rpm they pretty much go away as well.
i can pull #7 later and take a look but I don't expect to find any plug issue, that would be dumb luck

 

[j91z28d1]

ahh. huh.


not sure it would help you diagnosed it but be interesting to put the timing retard pid up to view. the knock sensors pick up mechanical stuff a pretty well, might show you something if you're getting a ton of retarded timing. especially under light load that shouldn't have any real knock.


I have read high rpm is ******* afm lifters, which is weird that they put them in the c7 corvettes. not that most it them get driven hard thou haha

 

[Charlie207]

I have KO2s on both of mine. Mid life they seem to be a booger to balance. I’m looking at options as well. I may pull them off thethirdtwin way early.

People sleep on Nokian A/T tires, but they are great, and offer excellent road/pavement life.

 

[Charlie207]

Made a thing to center the front timing cover. The kids don't use their little toy 3D printer, so I fired it up with a ThingVerse .stl, and made the overpriced tool for free.

EDIT: Also, the new harmonic balancer just arrived. Now I'm just waiting on the oil pickup tube clamp to button up the front of the engine.

 

[j91z28d1]

very nice

 

[Doubeleive]

still need to pull a plug so see if by some chance there is fowling but otherwise got a quote to do the left bank oem $2400 presuming the cam is ok
they can get it to right away, dealer told me $3-3300 and they are backed up for 2 weeks and are currently victims of the hack job so everything is being done without computers which is slowing them down, planning on a road trip in a couple weeks so I need it done.
+200 for the deeper diagnotic that needs to be done

 

[j91z28d1]

3k to pull 1 head and change 8 lifters with new afm lifters?

man what do shops get for a full delete kit these days? I feel like yours getting into full drop in stroker motor long block at that point.

 

[Doubeleive]

3k to pull 1 head and change 8 lifters with new afm lifters?

man what do shops get for a full delete kit these days? I feel like yours getting into full drop in stroker motor long block at that point.

I am sure there is a janky place around here that could do it cheaper but this is my daily and road trip vehicle I want at least some confidence no shortcuts are done, that shop I got the price from has been around for probably 50 years they used to do drag cars but some of the mechanics retired and they don't have equipment they used to have to work on the carbs

 

[j91z28d1]

the going rate is the going rate.
it's just the one side? and I guess you gotta put in afm lifters in it? everything always breaks at the wrong time


since it's a race shop, have you priced a stroker short block price? you make really like. the extra tq and reuse your heads?

 

[Doubeleive]

the going rate is the going rate.
it's just the one side? and I guess you gotta put in afm lifters in it? everything always breaks at the wrong time


since it's a race shop, have you priced a stroker short block price? you make really like. the extra tq and reuse your heads?

that's using oem parts, no I haven't looked at any engine options if I were to do anything I would throw a magnusen or something on it. I just want it back to running right.
I can swing the money with a credit card and only pay a one time fee of 4% which I can get back in credits on another card and I don't have to take a hit on my savings then I have a year to pay it off

 

[Doubeleive]

actually that shop has been around since 1932....a bit longer than I thought

 

[Doubeleive]

plug #5 with 50k on it which is one of the cyl giving me misfires yesterday while diagnosing, so I don't think it's fouled plugs

 

[Doubeleive]

It's mostly on #7

 

[j91z28d1]

@donjetman I'm sure is way better at reading plugs than me.. there's an art to it.

but all this specking might be a thing and lead to what I believe they call carbon tracking? basically the plug shorts from the deposits on it so it doesn't arc right. I've done it myself but it was a decent amount of pinging that caused mine.

if it was mine, I'd throw a cheap 3$ plug in it from a local auto parts store just incase. probably nothing but maybe. might even try an autolight of all things haha. there was a thread years about about false knock on a diy tuning board. 2 years long and at the end someone random said try an auto light and damned if that didn't cut the knock rate in half for no good reason.

 

[Doubeleive]

@donjetman I'm sure is way better at reading plugs than me.. there's an art to it.

but all this specking might be a thing and lead to what I believe they call carbon tracking? basically the plug shorts from the deposits on it so it doesn't arc right. I've done it myself but it was a decent amount of pinging that caused mine.

View attachment 431136


if it was mine, I'd throw a cheap 3$ plug in it from a local auto parts store just incase. probably nothing but maybe. might even try an autolight of all things haha. there was a thread years about about false knock on a diy tuning board. 2 years long and at the end someone random said try an auto light and damned if that didn't cut the knock rate in half for no good reason.

didn't look that close lol, already put it back in
here is a couple more zoomed in

 

[gooffeyguy]

Is that balls of aluminum on the center electrode in that top pic