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Discussion Starter #1
Hey folks. I'm about to burn this truck as its driving me insane. I can't figure out what's going on with my girlfriends LB7.

Truck currently has 201k miles on it. The engine has been replaced recently and has had this sputtering issue since we got it. No matter how light or heavy on the throttle, in park, the truck will not rev past 2k. It just sits at 2k sputtering. I had a problem with fuel in oil (lots of it) and I think I nailed that down. Here's what I've done:

Rebuild filter head
Replace all rubber fuel lines. Filter head, FICM and CP3 lines
Re sealed injectors with all new o rings and seals
Replaced high pressure lines
Installed FPRV plug
New Fuel Filter


I ran the truck with the upper covers off and used my buddies Solas Ultra to command full pressure. Found a problem injector that leaked from the inlet. Replaced injector

Today I unplugged the FPR and went to run it. Truck runs very rough, and revs to 2k and stays there, even at full pressure. Upon deceleration of engine speed from 2k, it has a hard time returning back to idle though it eventually gets back down there.

Anyone out there have any tips or ideas on what to look for next??
 

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Discussion Starter #2
Oh also, I ran a compression test and all cylinders were between 410psi and 425psi
 

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What about the fuel pressure sensor? I don't know much about the diesels yet as I just got bought mine, but that's just my guess. But it sounds like the computer is in "reduced engine power" I cleared mine by removing the NEG on the batteries for a minute.
 

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When you commanded the fuel pressure did the actual pressure follow the desired fuel pressure
 

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Discussion Starter #5
That's one thing I'm unsure of on that test. I was checking to make sure everything was clear under the hood and didn't see the scanner. However, before all this, I used my edge CTS and it did in fact follow desired rail pressure.

Here's one thing I did just find on the truck about 10 minutes ago. While it was running, I made sure it sputtered. Then, engine running, I began pumping the primer for about 30 seconds. Return to the pedal and it revs free, no sputter or hiccups..... ??

Sooooo could it be a cp3 issue, or issue elsewhere? It also does not lose prime..
 

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Mine did something similar wouldn't rev past 2k turned out to be my fuel filter jelled up have you changed it?
Could be a fuel leak or air going into the system I would check the return lines and filter housing.
Hope you get it figured out.
 

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Not positive, but I think that is a built in rev limiter when the truck is in Park. Once you hit 2000 rpm, the ecm is trying to govern the engine. I seem to recall my 04 LB7 will do this also.
 

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Just a shot in the dark but has this truck had the option done where you use the high idle option using the cruise control? If so from what I have read is if you don't turn this off it will not let the truck rev over 2000 rpm. Just a guess
 

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Discussion Starter #9
Im here in San Jose California, I'm probably the furthest away from fuel gel issues considering the high today was 76 degrees. It's also done this since last summer, during the 100 degree plus mark. It's just interesting that the problem subsided after
 

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I would guess to say it needs a new filter head or further diagnosis into the CP3.
 

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Discussion Starter #11
Update. I went out to start the truck after sitting. It was sputtering again. I turned the truck off, pumped the hell out of the primer and started it up and went for a drive. This time it didn't sputter AT ALL all the way to redline. Pulled smooth, no problems. So what the hell? I feel it's not a cp3 issue as the truck runs well once I get the hiccups out after pumping the primer. Could it be an air leak? It doesn't lose prime but somethings got to be goin on. No fuel leaks anywhere either. I rebuilt the filter head with new o rings and seals as it did leak before, but now it doesn't appear to be. Is there a way to test these things?
 

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I had similar issues with mine would not go over 2000 RPM sounded like a school bus. I changed the fuel pressure regulator fixed everything. The downside if you need to change the regulator if you dont cuss you will start. Good Luck
 

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When you commanded the fuel pressure did the actual pressure follow the desired fuel pressure
If your fuel pressure matches (desired vs. actual), a lift pump will prolly "fix" it. If u have a bad leak it will show when you add a lift pump. If it doesn't change anything your still good because your truck will benifet in the long wrong run with added filtration. If funds are tight try to pressure the fuel tank with a shop vac reversed into blower mode (make certain hose is clean first), any leaks should show up.
 

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You may have pinched the o ring in the filter head I've heard of that happening.
Also check the bleeder screw on the filter head I had a problem with the oring on mine leaking
 

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Yes this is correct, my 2002 lb7 is currently not revving past 2000rpm because of the high idle. when the high idle is left on it will not rev past 2000rpm; however, right now the truck still will not rev past 2000 rpm. I can not figure it out. I have completely took the high idle off and unplugged the batteries for an hour to try and reset the computer. All I can think of is that the ecm still thinks the high idle is on and I don't know how to override the ecm to think that the high idle is not on.
 

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If you can get it to run normally for a little while, that would probably rule out the CP3 or FPR, especially if desired vs. actual RP runs fairly close. Could the pickup in the tank be getting clogged? Sucks that fuel issues are so hard to nail down; almost as bad as electrical.
 

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Yes this is correct, my 2002 lb7 is currently not revving past 2000rpm because of the high idle. when the high idle is left on it will not rev past 2000rpm; however, right now the truck still will not rev past 2000 rpm. I can not figure it out. I have completely took the high idle off and unplugged the batteries for an hour to try and reset the computer. All I can think of is that the ecm still thinks the high idle is on and I don't know how to override the ecm to think that the high idle is not on.
Any codes stored, or boost leaks? If the truck went into limp mode for fuel or air restriction you will need to clear the codes to exit limp mode. This happened on my 01 all the time due to worn out fuel lines, reset the code and its back to normal until the next time the suck flat.
 

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Sucking air somewhere, if it doesnt lose prime I would "Think" the head is good. Maybe the filter has to much restriction? Just telling you what I would check. I would change the filter unless you already did it.
 
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