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Discussion Starter #21
Wish i logged the RPM on the pic above. Since i'm thinking it should have had 5psi of boost with the throttle at 80%???? I see 15 which is 1psi of boost.

I leak checked the hot side of the turbo held at 10psi so going to say no leaks. I have seen the boost go as high as 32psi on the scanner so that would be 14 - 32 = 18psi which seems normal from what i understand on an LB7 stock turbo.

Running out of ideas besides replacing big money items that may not fix anything. Like injector set, 64mm Turbo, Tuner...
 

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You may need to find someone with a Tech II and do some deep diving. Wouldnt start replacing more stuff yet until more investigation.
 

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Discussion Starter #23
I tried to read the stock ECM with HPTuners only to discover the ECM is not readable most likely tuner locked. Im waiting on a replacement ECM. Will go from there i guess.
 

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2001 Chevy Suburban LBZ 4x4
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Are you reading the number off the map sensor cause 14psi at idle is the atmospheric pressure so 32-14 would give you 18psi.
 

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2001 Chevy Suburban LBZ 4x4
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36 Posts
Have you tried replacing your fuel pressure relief valve. Sometimes it can open up early and you'll get low rail pressure
 

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Discussion Starter #26
Yes i'm reading the map for boost numbers. I have replaced the relief valve.

I'm waiting on a replacement ECM. I tried reading the ECM with HPtuners and found it is tuner locked. So hard to say what crap was loading into the stock ECM.

Will post results her as i go waiting on UPC.............
 

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2001 Chevy Suburban LBZ 4x4
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I remember on my dads lb7 when he had issues with low rail pressure he went through everything you've done including changing the cp3, fuel pressure regulator, rebuilt the fuel filter housing, capped the relief valve, installed a lift pump, had the ecm reflashed and had the low rail pressure parameters extended and after all that it turned out to be the injectors. Dont but cheap injectors or you can look at doing the work all over again after 20k miles
 

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Discussion Starter #28
New ECM installed HP Tuners up and running. Running out of ideas here truck is acting very strange.

--When you put the truck in gear it pushes very hard to start rolling in Drive or Rev.
--No codes are being generated.
--Trans was rebuilt by a local shop.
--Almost feels like truck is not using 1st gear ever. I logged with HP Tuners it is showing gear commanded etc all look correct, But sure feels like its not going to first gear. Seat of pants feels like it always starts out in second. Trying to figure out how to prove that besides put in 4 low and count shifts.
--Can log all sensors in HP Tuners but not sure what to look at all seem to be rading that i have tested.
--Once it get rolling out it goes like all hell.
 

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Discussion Starter #29
I think there is only 2 things left i can think of.

--Turbo not building boost soon enough to start commanding fueling.
--Some enomilly with the injectors which is just causing limp mode.

If i go after either will but quilty new parts.
 
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