Duramax Diesels Forum Truck of the Week
  #1  
Old 01-02-2018, 09:18 AM
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mamu mamu is offline
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Default lmm fuel knock misfire

hey guys,

i had a lmm come in with a fuel knock and bucking and jumping on the road. reduced engine power and barely would pull it self. showed 3 and 5 cylinder misfire on the computer but that was the only codes. heres what I've checked.

crank ring good and tight.
load tested and ohm tested all injector wires from ecm to injectors
swapped ecm and didn't change.
ran compression (all 375-400ish)
pulled injectors and had them tested...replaced 3

put it all back together and now 4 and 6 show misfire codes. at idle its smooth and fine but when you crack the throttle at about 925 rpm it starts knocking and missing. i can cut out #1 injector with the scanner and the fuel knock goes away. but it still misses.

all balance rates are -2.5 to +2.5 are the 2 worse the rest are -1 to +1

truck has whiteish blue smoke. smells like fuel. but honestly i don't have a clue. im to the point where i need anybodys thoughts and see if we can't stumble across the issue.

truck is 08 lmm 2500 crew cab. deleted with ppe. has been that way for over a year. rite before christmas this issue started. no other mods that i know of.

thanks
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2006 cc dually efi studs danville 2.5 drop in built trans fass
2005 ecsb efi ppe trans airdog 150 batmo
2007 crew cab dually ppe hot +2……stock.....sold
2002 rclb efi airdog 150……shop truck
1992 rcsb 6.0/nv4500 efi by black bear 9.25/11.5 solid axle conversion 37'' boggers (weekend warrior)

Last edited by mamu; 01-02-2018 at 09:20 AM. Reason: forgot truck mods
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  #2  
Old 01-02-2018, 09:38 AM
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Chevy1925 Chevy1925 is offline
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put the stock tune in it and see if the knock stops. it will still start and rev without the emissions crap hooked up on a stock tune
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BIG THANKS TO: Mike L, Steve, Trent, Guy, Dan, Ruben, Josh H, Scott, Brian and everyone else who has put a hand in to help me.

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Old 01-02-2018, 12:48 PM
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my old LMM did that when i hooked up the fuel pressure gauge just FYI , any Autometer fuel 0-30K would do it
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2015 GMC Denali 4X4 CC/SB 2500 LML
20" MOTOs
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2008 GMC 2500 (SOLD)
EFI,all deleted,rode hard,stayed together

2009 Chev 2500 (traded) EFI, all deleted, rode just as hard as her ^^^, stayed together
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Old 01-02-2018, 12:48 PM
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rail pressure
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2015 GMC Denali 4X4 CC/SB 2500 LML
20" MOTOs
Delete/EFI/5" straight soon to come




2008 GMC 2500 (SOLD)
EFI,all deleted,rode hard,stayed together

2009 Chev 2500 (traded) EFI, all deleted, rode just as hard as her ^^^, stayed together
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  #5  
Old 01-02-2018, 12:55 PM
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put truck back to stock. same thing.

truck will rev but it misses and shakes all the way through the rpm range.

checked rail pressure and it shows to be matched pretty consistent with desired.
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2006 cc dually efi studs danville 2.5 drop in built trans fass
2005 ecsb efi ppe trans airdog 150 batmo
2007 crew cab dually ppe hot +2……stock.....sold
2002 rclb efi airdog 150……shop truck
1992 rcsb 6.0/nv4500 efi by black bear 9.25/11.5 solid axle conversion 37'' boggers (weekend warrior)
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Old 01-02-2018, 02:06 PM
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Chevy1925 Chevy1925 is offline
don't know sh!t about IFS

 
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time to start looking at a broke crank then
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Quote:
Originally Posted by JoshH View Post
Mike L is my role model. I want to be like him when I grow up.
James

02 LL7 2500HD CC/LB dmax/alli "The Limo"

BIG THANKS TO: Mike L, Steve, Trent, Guy, Dan, Ruben, Josh H, Scott, Brian and everyone else who has put a hand in to help me.

best time to date: 12.39

motor died/bent rods = 3/11/11
back from the dead 7:04pm 4/9/2012

Limo is back in the garage, now driving a built chevy tracker
Tailgate Crew Member #4
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  #7  
Old 01-02-2018, 02:32 PM
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stibuilder stibuilder is offline
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Program the injector codes on all the injectors you replaced its the 13 digit number.
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  #8  
Old 01-03-2018, 05:50 AM
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yea we reprogrammed all the injectors. had 2 that wouldn't program. figured out they where plugged in wrong (4 an 6 was swapped) but all programming is done now.

a broke crank? this don't act like any other broke crank I've seen but ill check today and see.
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2006 cc dually efi studs danville 2.5 drop in built trans fass
2005 ecsb efi ppe trans airdog 150 batmo
2007 crew cab dually ppe hot +2……stock.....sold
2002 rclb efi airdog 150……shop truck
1992 rcsb 6.0/nv4500 efi by black bear 9.25/11.5 solid axle conversion 37'' boggers (weekend warrior)
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Old 01-04-2018, 04:21 PM
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checked crank. cant see any signs that its broke. turned it from front and read and theres not any play. it idles smooth now. but as soon as you get to the 925 rpm it goes crazy. I honestly have never seen this so I'm sure theres a sign somewhere I'm overlooking.
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2006 cc dually efi studs danville 2.5 drop in built trans fass
2005 ecsb efi ppe trans airdog 150 batmo
2007 crew cab dually ppe hot +2……stock.....sold
2002 rclb efi airdog 150……shop truck
1992 rcsb 6.0/nv4500 efi by black bear 9.25/11.5 solid axle conversion 37'' boggers (weekend warrior)
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Old 01-08-2018, 05:49 AM
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any one?
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2006 cc dually efi studs danville 2.5 drop in built trans fass
2005 ecsb efi ppe trans airdog 150 batmo
2007 crew cab dually ppe hot +2……stock.....sold
2002 rclb efi airdog 150……shop truck
1992 rcsb 6.0/nv4500 efi by black bear 9.25/11.5 solid axle conversion 37'' boggers (weekend warrior)
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Old 01-08-2018, 12:22 PM
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Are you able to monitor the crank and cam sensors when it starts running rough?
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Old 01-08-2018, 07:06 PM
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thats the only thing i haven't watched specific. like the cam ring came loose. but the rpm doesn't change when its acting dumb at idle. hard to tell. ill check the cam counts missed in the morning tho.
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2006 cc dually efi studs danville 2.5 drop in built trans fass
2005 ecsb efi ppe trans airdog 150 batmo
2007 crew cab dually ppe hot +2……stock.....sold
2002 rclb efi airdog 150……shop truck
1992 rcsb 6.0/nv4500 efi by black bear 9.25/11.5 solid axle conversion 37'' boggers (weekend warrior)
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Old 01-09-2018, 08:02 AM
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with truck running and missing it doesn't count any on the cam reference missed. but when i crank it up it will count to 33-35 before it starts and runs. but never goes back to 0 while running. but never goes up either.

still showing #1 cylinder misfire.
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2006 cc dually efi studs danville 2.5 drop in built trans fass
2005 ecsb efi ppe trans airdog 150 batmo
2007 crew cab dually ppe hot +2……stock.....sold
2002 rclb efi airdog 150……shop truck
1992 rcsb 6.0/nv4500 efi by black bear 9.25/11.5 solid axle conversion 37'' boggers (weekend warrior)
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  #14  
Old 01-09-2018, 02:43 PM
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With the 1 misfire I’m still betting you have harness issue, maybe ecm... how did you test the wiring?
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  #15  
Old 01-11-2018, 06:38 AM
mamumtsllc mamumtsllc is offline
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Quote:
Originally Posted by Burn Down View Post
With the 1 misfire I’m still betting you have harness issue, maybe ecm... how did you test the wiring?
I've changed ecm and it stays. I load tested all wires and checked resistance. Made sure they weren't rubbed together and jumping fire. I'll check them again to make sure.

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