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Duramax First Generation: 2001-2004 (LB7) Discuss the first generation (2001-2004 LB7) of the 6.6L Duramax diesel engine & associated components. Engine related discussion ONLY.

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Old 09-30-2012, 03:50 PM   #1 (permalink)
speak2mlv
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2001 LB7 sluggish on take off

I have a 2001 LB7 with 155,000 miles and am running pretty much stock. For quite a while it appears sluggish on take off. I timed myself 0-60 an got 14.6 and 13.8. This seems high to me. When I smash the pedal it feels like it is bogged down until around 30mph and then it will really move. However, occassionally it appears that it really responsive and there is not lag at all and it will really accelerate from start off. I have not timed when this does this because it happens less often and I do not know when it will. I have a brand new fuel filter and air filter but this problem has been consistent through many of these filter changes. I had a full set of new injectors installed by GM about 15,000 miles ago but this problem was happening before the injector replacement and I cannot tell any difference in the symptoms since they were replaced. I have had a compression test and it came back excellent. I have had the fuel pressure regulator tested and it tested good.

I am confused as to whether this may be a CP3 Pump, FPR (despite testing good), a turbo problem, allison 1000 problem or something else. Can anyone help?
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Old 09-30-2012, 08:22 PM   #2 (permalink)
TOTHEMAX!
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Are you producing boost? Does the truck smoke?
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Old 09-30-2012, 08:55 PM   #3 (permalink)
speak2mlv
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When I stomp on the pedal I do get some smoke but I don't think it is excessive. I only get some up to about 25mph and then none. I don't feel that I am getting boost up until 30mph or so.
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Old 10-01-2012, 01:36 AM   #4 (permalink)
tileman2003
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check for hole in boost tube above steering box.
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'03 D/A LB/EC LS/4X4
4'' Rancho lift 286 75 16's on eagle alloys, line-x.
full length nerf bars,
nice and stock...
injectors at 59,000mi...

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'99 Acura 3.2TL
'87 Pilgrim 8.5 TC
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Old 10-01-2012, 10:31 AM   #5 (permalink)
gmc502
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Quote:
Originally Posted by tileman2003 View Post
check for hole in boost tube above steering box.
agreed
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Old 10-01-2012, 12:06 PM   #6 (permalink)
Brimfield
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Why did you say pretty much stock? It helps to list any add ons to the Truck. Are you running a programer or chip.
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Old 10-01-2012, 09:07 PM   #7 (permalink)
speak2mlv
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I will check the boost tube for a leak tonight. The only changes I have made from stock is cut a bigger opening in the air intake box. Other than that everything is stock. I have no programmer of chips.
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Old 10-01-2012, 10:35 PM   #8 (permalink)
speak2mlv
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Ok...I checked the tube and there were a couple of significant rub marks on the tube. I don't think any of the rubs are all the way through the tube. However, I did find that the hose that connects to the tube just above the steeing shaft was not on all of the way and was in fact on at a slant. I put this back together correctly and test drove the truck. I did see improvement and there is virtually no smoke when I mash on the pedal from a dead start. So from this perspective there was improvement from this change. Nevertheless, I still feel like I do not have responsiveness when I initially stomp on the pedal. I clocked myself 0 to 60 several times and there was improvement but I will still in the 11.2 to 11.5 second range. Maybe I am wrong thinking I should be at least sub 10 sec with the truck having 155k miles. What do you all think?
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Old 10-01-2012, 11:07 PM   #9 (permalink)
tileman2003
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What size tires you running? just curious
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'03 D/A LB/EC LS/4X4
4'' Rancho lift 286 75 16's on eagle alloys, line-x.
full length nerf bars,
nice and stock...
injectors at 59,000mi...

'02 18' Bayliner
'99 Acura 3.2TL
'87 Pilgrim 8.5 TC
'90 4runner
'90 Suzuki dr 250
www.perrytile.net



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Old 10-01-2012, 11:12 PM   #10 (permalink)
speak2mlv
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265 75 16
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