Chevy/GMC Duramax 01-04 LB7 Discussion of Chevy and GMC Trucks with LB7 Duramax Turbo Diesel Engines

engine limping

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Old Sep 1, 2009 | 05:48 PM
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02 max's Avatar
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Default engine limping

hey guys need some help

Hooked my truck three times last Saturday and it would fall on its face at the 180' / 200' mark. I roll off the line, stand on it, then manually shift at aprox. 4000 rpm. At first I thought the tcm was overriding and shifting into fourth, so last pull left in second gear same issue, goes from 4200 to 2700 like someone flipped a switch. Has occasionally thrown an overboost code in the past, but nothing this time around. Had noticed it seemed a little week in fourth recently but I try not to run it to hard as trans is stock for the most part (trying to make it last till I can afford upgrade). Changed fuel filter tonight just to make sure, but no difference. Have one pull left this season and could use any suggestions. Truck would be competitive if I could get this issue taken care of.
 
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Old Sep 1, 2009 | 05:52 PM
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were you pulling in 4 hi or 4 low. and you have a quad tuner right?
 
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Old Sep 1, 2009 | 05:55 PM
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4low with quad set at 215
 
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Old Sep 1, 2009 | 05:57 PM
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Stock Allision transmission?
 
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Old Sep 1, 2009 | 06:00 PM
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has valve body portion of trango installed waiting on rest till i can afford converter
 
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Old Sep 1, 2009 | 06:01 PM
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Sounds like you might have Limped the Trans.
 
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Old Sep 1, 2009 | 06:04 PM
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i don't think so, whenever i've limped the trans in the past it throws a code and locks in third until i erase it
 
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Old Sep 1, 2009 | 06:09 PM
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I was almost thinking fueling issue, What fueling mod's do you have?
 
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Old Sep 1, 2009 | 06:20 PM
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modded cp3 (diy version), 160gph eldebrock lift pump lift pump (same as ppe) set for 11psi on the street and 15psi for pulling. Watched fuel gauge when it happens, pulls down to 3or4 at wide open bounces back to 9 when it limps (pressure pulled at factory service port).
 
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Old Sep 1, 2009 | 06:43 PM
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I've yet to have this type of complication without codes...I'm not sure exactly whats going on.
 
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