Duramax Diesels Forum Truck of the Week
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Old 06-04-2018, 08:37 AM
fl0w3n fl0w3n is offline
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Default Diagnosing shake at idle (not fpr)

02 LB7 ZF6, lotta miles, hard ones too.

New Bosch FPR when I got it, really smoothed out the idle compared to now. Before it was lopey, now it’s just shakey.
Injector rates don’t seem too bad with EFI Live, and checking with TorquePro app it’s just about the same numbers.
Passenger motor mount was shot, replaced that and it just barely helped. Haven’t done driver or trans mount yet.

I was thinking it was maybe the DMF in the ZF6, but reading up about that I don’t think it would be as driveable as it is if it was broken. Although I do hear a rattle at idle

I am suspicious of the harmonic balancer, either being spun on the crank or just missing chunks. I’ve got a new one, as well as a key repair kit on its way, I’ll do the water pump and check while I’m down there. However, in the video the balancer looks steady.

Can I get some ideas and help on diagnosing?

Screen shot of balance rates
https://imgur.com/a/RIxMtZ8.jpg
https://imgur.com/a/5CBigy1.jpg


Attached Images
File Type: png FF7E0572-E6B1-407A-BF0D-A9E4598C0490.png (123.0 KB, 12 views)
File Type: png 2DF610D8-E56E-490B-9B0C-FEDFD46BBD80.png (122.1 KB, 12 views)
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2002 LB7/ZF6 CCSB Sierra 4x4
340k miles
Stock...for now

Plans:
KP D60 front, ORD leafs front/rear, Twin Stick NP205, 4.56 gearing locked rear, PSC steering/hydro assist , 37"s on H1 wheels, Titan or Aerotank replacement

SAC45% Injectors, SB SD clutch, Kennedy pump and filter heads, S&B intake, ProFab up/down pipe, manifolds, Mild Tune from Rob

Last edited by fl0w3n; 06-04-2018 at 10:10 AM.
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Old 06-04-2018, 09:28 AM
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Injectors is my guess. How many miles on them? Who’s injectors?

I have a little shake with my ii injectors in my 05’. I have run a bunch of seafoam and optilube, the shake is almost gone. My balance rates looked pretty good with 5 being at-5 when I first got it. Now it’s at -3, gotta love ii...
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Old 06-04-2018, 09:53 AM
fl0w3n fl0w3n is offline
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Quote:
Originally Posted by Burn Down View Post
Injectors is my guess. How many miles on them? Whos injectors?

I have a little shake with my ii injectors in my 05. I have run a bunch of seafoam and optilube, the shake is almost gone. My balance rates looked pretty good with 5 being at-5 when I first got it. Now its at -3, gotta love ii...
No idea whos injectors, previous owner said they had been replaced but I doubt they were some quality units or done right.

350k miles on the truck. Previous owner said cp3 only has 20k miles on it, again not sure brand or quality of the part that was installed. Its an old farm truck, worked hard and put away wet type life.

What is ii? Ive run AC Delco upper injector cleanse through, and throw optilube in the tank for now. Im planning on trying AC Delco again soon. I think the truck sat for a while, and now that Ive been using it and logging some miles it seems to be waking up a little. But the rates look good from what Im reading, except a random 6.8 reading on one of the torque pro screen shots.
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2002 LB7/ZF6 CCSB Sierra 4x4
340k miles
Stock...for now

Plans:
KP D60 front, ORD leafs front/rear, Twin Stick NP205, 4.56 gearing locked rear, PSC steering/hydro assist , 37"s on H1 wheels, Titan or Aerotank replacement

SAC45% Injectors, SB SD clutch, Kennedy pump and filter heads, S&B intake, ProFab up/down pipe, manifolds, Mild Tune from Rob
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Old 06-04-2018, 10:16 AM
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II (industrial injection)... lb7’s are hard on injectors, plan on doing them soon. Any white smoke cold or warm? Tuned or stock?
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Old 06-04-2018, 10:47 AM
fl0w3n fl0w3n is offline
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Quote:
Originally Posted by Burn Down View Post
II (industrial injection)... lb7s are hard on injectors, plan on doing them soon. Any white smoke cold or warm? Tuned or stock?
My plan is LDS sac45s soon.

No white smoke, no fuel halo in oil when I drop it on a white paper towel. Stock.

It seems like signs point to the injectors being OK... but Ill be replacing them eventually any ways.
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2002 LB7/ZF6 CCSB Sierra 4x4
340k miles
Stock...for now

Plans:
KP D60 front, ORD leafs front/rear, Twin Stick NP205, 4.56 gearing locked rear, PSC steering/hydro assist , 37"s on H1 wheels, Titan or Aerotank replacement

SAC45% Injectors, SB SD clutch, Kennedy pump and filter heads, S&B intake, ProFab up/down pipe, manifolds, Mild Tune from Rob
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Old 06-04-2018, 11:10 AM
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What does the cam and crank sensor signals look like? Does it smooth out just off idle?
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Old 06-04-2018, 12:28 PM
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I would shut off each injector individually and see if the shake goes away.
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Old 06-04-2018, 12:59 PM
fl0w3n fl0w3n is offline
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Quote:
Originally Posted by Burn Down View Post
What does the cam and crank sensor signals look like? Does it smooth out just off idle?
Good question, I forgot to bring that up. Idle is right around 600rpm and if I bring it up to about 8-900 it gets a tiny bit rough and just a little stumbly I feel like. I’ll try and make a video of that. At cruising or freeway speed, I can’t discern any shake over the general rough ride the shot suspension provides. Seems to cruise up to 85mph without much complaint. Another reason I’m hesitant about it being balancer, I feel like it would get worse with RPM

How can I check cam and crank sensor signals? Will torque app do that?
Quote:
Originally Posted by Brent@LDS View Post
I would shut off each injector individually and see if the shake goes away.
I assume I’ll need to do that with EFI Live? My friend is the one who had it on his laptop, I’ll need to do that next time I’m at his place.

Unless there’s another way to do it?
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2002 LB7/ZF6 CCSB Sierra 4x4
340k miles
Stock...for now

Plans:
KP D60 front, ORD leafs front/rear, Twin Stick NP205, 4.56 gearing locked rear, PSC steering/hydro assist , 37"s on H1 wheels, Titan or Aerotank replacement

SAC45% Injectors, SB SD clutch, Kennedy pump and filter heads, S&B intake, ProFab up/down pipe, manifolds, Mild Tune from Rob
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Old 06-04-2018, 01:07 PM
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I use a scan tool for the crank/cam signals. Not sure what your app shows? Efi or a scan tool can shut the injectors off individually.
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Old 06-05-2018, 11:53 AM
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Your balance rates look OK, but the warning sign is the main fuel rate is only 4.6mm. It should be almost double that for a stock tune, I believe. What that means is your injector are all in similar condition (balance rates tell how uniform injectors are), but overall condition is poor. They all appear to be weeping fuel, and the computer is compensating by reducing the desired fuel amount.

My numbers come from an automatic in neutral. The ZF6 might have less parasitic loss in neutral, but I wouldn't think half. I think worn injectors are your problem here.
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Old 06-05-2018, 12:08 PM
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bet its the dmf I have changed several that where still being driven with a shake like that and worse.
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06 lbz ec/sb. stock motor, Danville 4094s2r, built trans by me, limitless 1078 converter, 60% sticks, S&S 12mm pump. dyno tuned by mark @ Danville. 775hp 1383ftlb

best so far. 11.440 @ 118.12 1.623 60ft

06 lbz rc/fb dually work truck. Danville tuned
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Old 06-05-2018, 01:32 PM
fl0w3n fl0w3n is offline
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Quote:
Originally Posted by DAVe3283 View Post
Your balance rates look OK, but the warning sign is the main fuel rate is only 4.6mm. It should be almost double that for a stock tune, I believe. What that means is your injector are all in similar condition (balance rates tell how uniform injectors are), but overall condition is poor. They all appear to be weeping fuel, and the computer is compensating by reducing the desired fuel amount.

My numbers come from an automatic in neutral. The ZF6 might have less parasitic loss in neutral, but I wouldn't think half. I think worn injectors are your problem here.
That makes a lot of sense. I was kind of suspecting that.
Like Ive mentioned I have been figuring on doing SAC45s, so its not crushing information to hear that. I think Ill still try AC Delco one more time.

With that being said, if all injectors are pretty evenly worn, why would it be causing the shake?
__________________
2002 LB7/ZF6 CCSB Sierra 4x4
340k miles
Stock...for now

Plans:
KP D60 front, ORD leafs front/rear, Twin Stick NP205, 4.56 gearing locked rear, PSC steering/hydro assist , 37"s on H1 wheels, Titan or Aerotank replacement

SAC45% Injectors, SB SD clutch, Kennedy pump and filter heads, S&B intake, ProFab up/down pipe, manifolds, Mild Tune from Rob
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Old 06-05-2018, 01:33 PM
fl0w3n fl0w3n is offline
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Quote:
Originally Posted by Tothemax View Post
bet its the dmf I have changed several that where still being driven with a shake like that and worse.
How can I check to confirm?
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2002 LB7/ZF6 CCSB Sierra 4x4
340k miles
Stock...for now

Plans:
KP D60 front, ORD leafs front/rear, Twin Stick NP205, 4.56 gearing locked rear, PSC steering/hydro assist , 37"s on H1 wheels, Titan or Aerotank replacement

SAC45% Injectors, SB SD clutch, Kennedy pump and filter heads, S&B intake, ProFab up/down pipe, manifolds, Mild Tune from Rob
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Old 06-05-2018, 02:37 PM
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you can take the starter out and use a flash light and a pray bar to see if the ring gear moves side to side. there is usually a lot of iron rust dust when there broken
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2017 l5p cc/sb ltz z71 (stormtrooper edition)


06 lbz ec/sb. stock motor, Danville 4094s2r, built trans by me, limitless 1078 converter, 60% sticks, S&S 12mm pump. dyno tuned by mark @ Danville. 775hp 1383ftlb

best so far. 11.440 @ 118.12 1.623 60ft

06 lbz rc/fb dually work truck. Danville tuned
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Old 06-05-2018, 04:37 PM
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Quote:
Originally Posted by fl0w3n View Post
With that being said, if all injectors are pretty evenly worn, why would it be causing the shake?
Because they are weeping fuel all the time, not just on the compression stroke.

Check the DMF, maybe that's it. I'm not very familiar with the manual trucks, so that could well be the issue.

Sent from my Cat S60 using Tapatalk
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