Loosing boost while pulling

2004LB7

Super Moderator
Staff member
Dec 15, 2010
7,104
2,207
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Norcal
LB7s don't suffer from leaking relief valves like the other years. It is unlikely that is your issue
 

I_B_RAGZ

New member
Nov 1, 2018
13
0
0
Pine valley, CA
Fast03 I will try that this weekend.. and Dave I tried deleting my ppe and my boost gauge and brought them back one at a time but even with no gauge and no valve i still felt the power loss come and go.. it’s really starting to piss me off and before spending a grand on the edge programmer and monitor I am trying to go thought every possible thing on the truck before I chip or re-chip it if it’s all ready tuned.. all my balance rates we normal when we checked them last which was a couple months ago.. the only thing I’ve found is that 7,000 psi drop..

What have you done to push 44psi and 27,000??


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I_B_RAGZ

New member
Nov 1, 2018
13
0
0
Pine valley, CA
That would push a CEL correct?? And all that would be read off the map sensor right? I’ve got the 3 bar stock map sensor in there is there one I can get that would read more??


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fast03

Active member
Jun 15, 2008
1,201
6
38
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Rancho Cucamonga
Are you still running the stock wastegate? If so, that might be the problem too? To et the stock wastegate past 25psi, you would need to modify it to keep it from popping open.

I had a larger Turbo on mine with no wastegate, custom intake, manifolds, downpipe to get to 44psi.

Do a search for bigger turbos for LB7 and add a lift pump to push fuel to the CP3
 

I_B_RAGZ

New member
Nov 1, 2018
13
0
0
Pine valley, CA
Yes as far as I kno it’s a stock wastegate. Empty I can push up to 26-28 and hold it for as long as I need yet as soon as I put a heavy load is when it’s starting to act up


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DAVe3283

Heavy & Slow
Sep 3, 2009
3,729
297
83
Boise, ID, USA
We need to get some data logs. Without data, we are all just guessing. Sure, we might stumble upon the problem and solution, but we might not...

If the truck is tuned, it might be setting the overboost limp mode and NOT setting the check engine light, depending on how it is tuned. It might be a good idea to verify the tune is stock before continuing, since you believe this to be a stock motor. If the tune turns out to be modified, then the solution is to either return it to stock, or modify it further to work for your setup.

Let us know the data when you hear back from your friend with the scan tool, because I'm out of meaningful guesses at this point.
 

I_B_RAGZ

New member
Nov 1, 2018
13
0
0
Pine valley, CA
I’ll get you more data hopefully soon he just told me he didn’t save so his comp didn’t retain it.. so when I get back from my hunting trip on Sunday I’ll make a run or two with it early next week and check back. Thanks again for the suggestions and hopefully I can get this prob to go away


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I_B_RAGZ

New member
Nov 1, 2018
13
0
0
Pine valley, CA
Hey guys just an update I did what fast03 told me to do and dropped a gear and stayed right about 22-23 on the boost gauge and didn’t ever loose it when I strived for 24-28 is when it started going on and out.. just a quick update from what I figured out this last trip while towing still trying to get time in the shop to make some more data numbers for you guys.. thanks again


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