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Thread: 02 CCSB LB7 severe lack of power (like a 4cyl)

  1. #1
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    Default 02 CCSB LB7 severe lack of power (like a 4cyl)

    I have a truck that I bought a while back with some preexisting problems. 02 2500HD LB7
    The main problem is the thing can't get out of its own way. When stone cold, it barely responds to throttle input, barely comes off idle even when floored. As it warms up it gets better, but acts like it is limited to 1/4 throttle or less other than trans shifts late or kicks down on heavy throttle input.
    It starts easily when cold and runs smooth with no unusual noises. No CEL ever.
    No smoke and 11 psi is the most boost I have ever seen.
    Almost tolerable it I load level 4 tune, but only with heavy input.
    My bone stock LB7 3500 flatbed running on 7cyl has way more power. It has a valve train problem.. :-(
    I have Torque Pro for logging, but it has its limits. Can't afford EFI Live yet.

    New Fuel filter (Dealer tested for restriction in fuel system @ 2hg)
    Tested Rail Pressure and it scales properly and Demand / Actual stay close.
    Injector Balance is within spec. (Injector Age unknown) Not Making Oil!
    PO did head studs 30k ago and Truck has 210k on it. (Said He couldn't afford to do the injectors then.
    Checked engine harness connectors and 1 pin was pushed in a little, but no change.
    Cleaned MAF and swapped with other truck, No change.
    MAP Seems to scale fine ( Maybe I should swap with known good?) Cleaned, no help.
    New Batteries and have tried another pair.
    Currently set to stock and ECM was updated at dealer recently with no change in power.
    The only think tech said was MAF not scaling to 450? I was able to get there but it took a while. Cleaned / Replaced made no difference.
    Had an AFE intake on it, switched to stock and noticed a slight change, but not much.
    Changed Trans Filter and topped off ATF as I heard that could affect it.
    Exhaust is a 4" MBRP SS Catback system so no restriction there.
    Not California model so no EGR.

    I am at a loss why it refuses to give it fuel, like something is holding it back. Anyone nearby have EFI Live or a tech 2? I can only do basic checking and logging with Torque Pro and I can't afford to go back to the dealer or throw parts at it. I have spent many a night researching and testing only to come up empty handed so far. Maybe if I get a chance I will recheck or swap out MAP and even the AP? Sensor. I believe they both show the same with key on.

    Any help solving this would be greatly appreciated...
    02 Chevy CCSB D/A, PPE Tuner, MBRP 4"
    95 Chevy k2500 6.5td mostly stock.
    95 Chevy C3500HD Dump box 6.5td 4" exhaust.
    85 K20, 6.2, T400, Bone Stock.
    85 K10 Blazer, 6.2 performance rebuild, 700r4.
    97 VW Jetta TDI, PP520 Nozzles = Fun 2 Drive.
    85 VW Golf 1.6 Diesel, 5 speed.

  2. #2
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    Brakes sticking? Check for free-turning wheels. The E-brake may be stuck. It's happened before.

    Other than that, it sounds like you'll need some hands on. Other than checking for actual fuel flow (collapsed line, other restriction), looks like you covered the basics.
    1985 Blazer 6.2
    2001 GMC 2500HD D/A
    dmaxmaverick@thedieselpage.com

  3. #3
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    No problems with the brakes. It is even sluggish to rev the engine with no load. I just did some more logging to look at fuel rate and it looks like the ECM is holding back on fueling. Swapped MAP with other truck and seemed to help ever so slightly and was able to get 15psi if I floored it long enough uphill. It is a fueling issue for sure, just can't figure out why. Seems like something is telling it to limit fuel??? Rail pressure was holding at 22k and even saw 24k momentarily under load up a hill, so that would eliminate and fuel restrictions, leaking injectors or weak pump.
    02 Chevy CCSB D/A, PPE Tuner, MBRP 4"
    95 Chevy k2500 6.5td mostly stock.
    95 Chevy C3500HD Dump box 6.5td 4" exhaust.
    85 K20, 6.2, T400, Bone Stock.
    85 K10 Blazer, 6.2 performance rebuild, 700r4.
    97 VW Jetta TDI, PP520 Nozzles = Fun 2 Drive.
    85 VW Golf 1.6 Diesel, 5 speed.

  4. #4
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    I finished more logging with Torque Pro on my other truck and now wondering if it is either bad FICM (Wouldn't it throw a code?) or maybe rust and junk plugging the injectors from when PO did the head studs? I would think if it was rust and junk in the injectors that the balance rates would be all over and in the + side due to trying to add fuel unless the restriction is not affecting it at idle? Any thoughts on this?
    02 Chevy CCSB D/A, PPE Tuner, MBRP 4"
    95 Chevy k2500 6.5td mostly stock.
    95 Chevy C3500HD Dump box 6.5td 4" exhaust.
    85 K20, 6.2, T400, Bone Stock.
    85 K10 Blazer, 6.2 performance rebuild, 700r4.
    97 VW Jetta TDI, PP520 Nozzles = Fun 2 Drive.
    85 VW Golf 1.6 Diesel, 5 speed.

  5. #5
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    Cool

    Another thought on this is possible air ingestion in fuel. Normally this would cause hard starting and other symptoms, but dealer tech said vacuum on fuel port was 2hg which could indicate an air leak? One thing I noticed is at one stop on my way home which is on a hill and I coast quite a ways to the stop and it feels like it has a lot more power and more responsive when I take off from there. Going to try a clear hose on feed line and look for air bubbles. Seems like this or FICM going bad, but everyone says FICM rarely has problems.

    Stay tunes for more results...
    02 Chevy CCSB D/A, PPE Tuner, MBRP 4"
    95 Chevy k2500 6.5td mostly stock.
    95 Chevy C3500HD Dump box 6.5td 4" exhaust.
    85 K20, 6.2, T400, Bone Stock.
    85 K10 Blazer, 6.2 performance rebuild, 700r4.
    97 VW Jetta TDI, PP520 Nozzles = Fun 2 Drive.
    85 VW Golf 1.6 Diesel, 5 speed.

  6. #6
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    The fuel system is under vacuum from the tank through the filter all the way to the high pressure fuel pump. If there's a leak in that vacuum system, it'll suck air in.

    It's been said that a lift pump (and extra filtration)at the tank will help things live longer. It will certainly make any fuel line leaks obvious by pushing fuel out of the leaky area instead of sucking air in. Take a look at Kennedydiesel.com to see what he offers for a lift pump/filtration system. He's a member/vendor here and stands behind what he sells.

    What kind of fuel filter are you using (OEM or aftermarket)? Lots of aftermarket filter cans use plastic housing instead of metal and have reportedly been prone to leak at the gasket. Even with the GM metal can, you've got to make sure the O ring gasket is properly in place or it'll leak.

    A clear section of fuel line will be a good diagnostic tool. Let us know what you find!

    (shamelessly stealing an image of a fuel pressure guage with and without a lift pump):


    How's the truck run with a loose fuel cap? If the tank isn't venting properly you could be building up vacuum in the tank, which could lead to collapsed fuel lines and fuel starvation.

    I'd be looking for another dealer tech... It doesn't sound like the one you've got now quite knows how the OEM system works.
    Last edited by rapidoxidationman; 03-07-2015 at 17:45.

  7. #7
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    Well, spent a lot of time on it again today.
    Swapped FICM with known good.... No change
    This was after installing a clear line between the FICM and Filter housing to check for air leaks. Was getting a ton of air for a while, but eventually that mostly stopped.
    Got dark before I could try the clear hose after filter housing. That and the hose is a b!tch to get at.
    Filter is from local GM dealer. Had Napa plastic on it before, but no change after new OEM filter was installed.
    If I had the money, I would install a lift pump, but currently unemployed and broke.
    This is incredibly frustrating since all logging indicates no fueling problems.
    I am aware of Kennedy Diesel and the great products he carries and has developed, just can't afford them right now. I wish I had his LB7 tune, at least once the current problem is fixed.
    I am well versed in diesels and understand the workings of a Duramax from massive amounts of research, just lack the experience.
    Have had and worked on tons of VW diesels new and old as well as 5.7 olds, 6.2 and 6.5td rigs. I have gained a lot of knowledge reading the forums and wish I had time to contribute more on here.
    Anyway, tomorrow is a new day...
    I just don't see it being injectors or the pump and the balance rates are good and it maintains pressure under load. That kind of eliminates a lot of stuff.

    BTW: I just installed a new OEM and correct fuel cap because it had a gasser cap on it. Running with cap loose did nothing as well.

    One thing I might add is that even just sitting there revving the engine with no load it is noticeably sluggish compared to my other stock LB7 running on 7 cyl...
    02 Chevy CCSB D/A, PPE Tuner, MBRP 4"
    95 Chevy k2500 6.5td mostly stock.
    95 Chevy C3500HD Dump box 6.5td 4" exhaust.
    85 K20, 6.2, T400, Bone Stock.
    85 K10 Blazer, 6.2 performance rebuild, 700r4.
    97 VW Jetta TDI, PP520 Nozzles = Fun 2 Drive.
    85 VW Golf 1.6 Diesel, 5 speed.

  8. #8
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    Have you data logged the gas pedal to see if the ecm is seeing the full range of voltages? I would also try a known good ecm.You would have to go through the vats learn process unless you have acess to a tech2.

    Jay
    2023 Tahoe 3.0l diesel
    2013 Harley Switchback
    2021 Ram 2500 6.7l (sold)
    2018 Chevy Traverse (sold)
    2021 Silverado 3.0l LM2 (sold)
    2019 GMC Sierra 6.2l (sold)
    2019 Colorado ZR2(sold)
    2017 2500HD CC D/A (sold)
    2015 1500 CC High Country 6.2l (sold)
    2010 Chev 2500HD CC D/A (sold)
    2013 Chev 2500HD CC D/A (sold)
    2006 Chev 3500 CC D/A (sold)
    2005 Harley Ultra Classic (sold)

  9. #9
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    I stated in a prior post that the pedal scales properly. Had swapped ECM with no change as well. It's handy having a truck that I can swap parts with, but so far I have been able to make very small inprovements, but overall it is far from normal.
    Going to check return line for restriction and more checking for air leaks.
    these things take time...


    Don't mistake the "newbie" under my title as being a newbie with diesels, I'm well versed in diesels and electroncs. I do appreciate any input as sometimes it is something simple that was overlooked.
    02 Chevy CCSB D/A, PPE Tuner, MBRP 4"
    95 Chevy k2500 6.5td mostly stock.
    95 Chevy C3500HD Dump box 6.5td 4" exhaust.
    85 K20, 6.2, T400, Bone Stock.
    85 K10 Blazer, 6.2 performance rebuild, 700r4.
    97 VW Jetta TDI, PP520 Nozzles = Fun 2 Drive.
    85 VW Golf 1.6 Diesel, 5 speed.

  10. #10
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    Quote Originally Posted by Diesel Krazy View Post
    No problems with the brakes. It is even sluggish to rev the engine with no load. I just did some more logging to look at fuel rate and it looks like the ECM is holding back on fueling. Swapped MAP with other truck and seemed to help ever so slightly and was able to get 15psi if I floored it long enough uphill. It is a fueling issue for sure, just can't figure out why. Seems like something is telling it to limit fuel??? Rail pressure was holding at 22k and even saw 24k momentarily under load up a hill, so that would eliminate and fuel restrictions, leaking injectors or weak pump.
    Do you have a boost gage? Or was this reported by the PCM, read on your scanner? 15 PSI is (minimally) respectable, if read from the gage, and the engine should be making power. NOT so, if reported via the PCM. It's barely above atmospheric pressure (1 BAR), at sea level (15-14.7=0.3 PSI, with a margin of error, may equal zero).

    Check the wastegate for operation. If it's stuck open, or not closing for any reason, no boost, no power.
    1985 Blazer 6.2
    2001 GMC 2500HD D/A
    dmaxmaverick@thedieselpage.com

  11. #11
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    The boost is corrected for atmospheric pressure. No gauge, but logging both trucks there is a big difference in boost. The other truck hits 22psi and spends a lot of time at 20+ under load. The truck in question briefly peaks at 10 - 15 but mostly sits at 5-9 while trying to get up to speed. I don't think boost is even an issue because no load revving of the engine should produce very little boost and it is noticeably unresponsive just trying to rev while in Park. My other truck revs much quicker and it is bone stock with 1 dead hole.

    I should also reiterate that if I load level 4 on the PPE (120 hp?) Have not tried level 5, 2 or 3 give lesser improvements. it wakes it up to almost tolerable except off idle and low load or hills without having to push it hard to start making some power.

    Didn't get time to work on it today due to GF and having severe back pain again. Probably will get back to it in a few days. Will keep updating the thread as I feel this is a somewhat unusual problem as it has no other symptoms besides being slower than a Mercedes 240D.

    I tried to log the fueling rate, but the only thing I can get data on is PID ff125d labeled "Fuel Flow Rate" in units/hr (GPH I think?) and it hits around 3/4 of the good trucks numbers IIRC. I'm thinking that may be some other measurement or calculated estimate???

    Who knows, just going to keep at it til I either get fed up or figure it out. TBC - School of hard knocks...Class Dismissed!
    02 Chevy CCSB D/A, PPE Tuner, MBRP 4"
    95 Chevy k2500 6.5td mostly stock.
    95 Chevy C3500HD Dump box 6.5td 4" exhaust.
    85 K20, 6.2, T400, Bone Stock.
    85 K10 Blazer, 6.2 performance rebuild, 700r4.
    97 VW Jetta TDI, PP520 Nozzles = Fun 2 Drive.
    85 VW Golf 1.6 Diesel, 5 speed.

  12. #12
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    This is curious. It's defueling to the point it has little power, like limp mode, but isn't throwing a related code. That leads me to suspect the aftermarket programmer. Try removing it (completely, physically, not just deprogrammed) and start at the beginning. If it is still that bad, it should throw some codes, without the PPE running interference. Or, as I've seen many times, that may be the problem, but they've almost all been the Edge units, and I've not seen this with PPE's.
    1985 Blazer 6.2
    2001 GMC 2500HD D/A
    dmaxmaverick@thedieselpage.com

  13. #13
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    Defueling is indeed what it acts like, but never any codes. Just to clarify I unloaded the PPE tune and then had the dealer update the PCM to eliminate any corruption in the ECM. At the same time I updated the PPE with the latest program from their site to make sure it was clean as well. Truck was no better after ECM update and I tried many things before ever loading PPE back on to it again. I've heard of a Duraminimizer and it sounds one possible explanation, but I see no other toys plugged in anywhere. From what I could tell, they plug into the harness by the master cylinder and there is nothing there.

    Back problems are keeping me from doing much at the moment.
    02 Chevy CCSB D/A, PPE Tuner, MBRP 4"
    95 Chevy k2500 6.5td mostly stock.
    95 Chevy C3500HD Dump box 6.5td 4" exhaust.
    85 K20, 6.2, T400, Bone Stock.
    85 K10 Blazer, 6.2 performance rebuild, 700r4.
    97 VW Jetta TDI, PP520 Nozzles = Fun 2 Drive.
    85 VW Golf 1.6 Diesel, 5 speed.

  14. #14
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    Quote Originally Posted by DmaxMaverick View Post
    This is curious. It's defueling to the point it has little power, like limp mode, but isn't throwing a related code. That leads me to suspect the aftermarket programmer. Try removing it (completely, physically, not just deprogrammed) and start at the beginning. If it is still that bad, it should throw some codes, without the PPE running interference. Or, as I've seen many times, that may be the problem, but they've almost all been the Edge units, and I've not seen this with PPE's.
    DK:
    When you say "unloaded" does it mean you actually REMOVED the programmer?

  15. #15
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    Yes, there is no reason to leave it plugged in otherwise. Except maybe to view diags, but I am using Torque Pro for that mostly. As I said, I even had the ECM updated and the PPE Programmer was not connected for quite some time afterwards while I was checking things out. Therefore the PPE programmer is not a factor whatsoever in this problem.
    02 Chevy CCSB D/A, PPE Tuner, MBRP 4"
    95 Chevy k2500 6.5td mostly stock.
    95 Chevy C3500HD Dump box 6.5td 4" exhaust.
    85 K20, 6.2, T400, Bone Stock.
    85 K10 Blazer, 6.2 performance rebuild, 700r4.
    97 VW Jetta TDI, PP520 Nozzles = Fun 2 Drive.
    85 VW Golf 1.6 Diesel, 5 speed.

  16. #16
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    Maybe a worn turbo? Clearances to great at the impeller to create boost.

  17. #17
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    I don't think boost is an issue as it should have more power that it does with no boost. My old 6.2 N/A truck has way more power. It is definitely a fueling issue. If I had a tech II or EFI Live to log the fuel rate I might be able to see something, but all I have available is Torque Pro which has very limited support on the DMax. Anybody have a list of PIDs for a LB7? I have some, but the fueling PID does not seem to work. I was able to get Fuel Rail Pressures working on it though.
    02 Chevy CCSB D/A, PPE Tuner, MBRP 4"
    95 Chevy k2500 6.5td mostly stock.
    95 Chevy C3500HD Dump box 6.5td 4" exhaust.
    85 K20, 6.2, T400, Bone Stock.
    85 K10 Blazer, 6.2 performance rebuild, 700r4.
    97 VW Jetta TDI, PP520 Nozzles = Fun 2 Drive.
    85 VW Golf 1.6 Diesel, 5 speed.

  18. #18
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    Quote Originally Posted by Diesel Krazy View Post
    I have a truck that I bought a while back with some preexisting problems. 02 2500HD LB7
    The main problem is the thing can't get out of its own way. When stone cold, it barely responds to throttle input, barely comes off idle even when floored. As it warms up it gets better, but acts like it is limited to 1/4 throttle or less other than trans shifts late or kicks down on heavy throttle input.
    It starts easily when cold and runs smooth with no unusual noises. No CEL ever.
    No smoke and 11 psi is the most boost I have ever seen.
    Almost tolerable it I load level 4 tune, but only with heavy input.
    My bone stock LB7 3500 flatbed running on 7cyl has way more power. It has a valve train problem.. :-(
    I have Torque Pro for logging, but it has its limits. Can't afford EFI Live yet.

    New Fuel filter (Dealer tested for restriction in fuel system @ 2hg)
    Tested Rail Pressure and it scales properly and Demand / Actual stay close.
    Injector Balance is within spec. (Injector Age unknown) Not Making Oil!
    PO did head studs 30k ago and Truck has 210k on it. (Said He couldn't afford to do the injectors then.
    Checked engine harness connectors and 1 pin was pushed in a little, but no change.
    Cleaned MAF and swapped with other truck, No change.
    MAP Seems to scale fine ( Maybe I should swap with known good?) Cleaned, no help.
    New Batteries and have tried another pair.
    Currently set to stock and ECM was updated at dealer recently with no change in power.
    The only think tech said was MAF not scaling to 450? I was able to get there but it took a while. Cleaned / Replaced made no difference.
    Had an AFE intake on it, switched to stock and noticed a slight change, but not much.
    Changed Trans Filter and topped off ATF as I heard that could affect it.
    Exhaust is a 4" MBRP SS Catback system so no restriction there.
    Not California model so no EGR.

    I am at a loss why it refuses to give it fuel, like something is holding it back. Anyone nearby have EFI Live or a tech 2? I can only do basic checking and logging with Torque Pro and I can't afford to go back to the dealer or throw parts at it. I have spent many a night researching and testing only to come up empty handed so far. Maybe if I get a chance I will recheck or swap out MAP and even the AP? Sensor. I believe they both show the same with key on.

    Any help solving this would be greatly appreciated...
    I'm not sure why the previous owner would have done head studs just out of the blue? Odds are that when the injector lines were removed and reinstalled they dropped a bunch of rusty junk in the inlet bowls of the injectors and that is what is giving it fits. It just cannot deliver the volume that it needs to make HP.


    Details here: http://www.kennedydiesel.com/docs/Du...0Corrosion.pdf
    Kennedy Diesel-owner
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  19. #19
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    I have thought about the injectors having crud in them from being worked on, but wouldn't balance rates be all over the board as they should not all be restricted the same? Also, why would it have significantly more power if I load a tune from the PPE? I really can't afford to do injectors right now, and don't like throwing parts at a problem unless there is a high probability of success in doing so.
    I would assume if this is indeed the problem, I'm looking at new injectors and lines both?
    Any real life symptoms described on one that was found to be badly plugged for comparison?
    02 Chevy CCSB D/A, PPE Tuner, MBRP 4"
    95 Chevy k2500 6.5td mostly stock.
    95 Chevy C3500HD Dump box 6.5td 4" exhaust.
    85 K20, 6.2, T400, Bone Stock.
    85 K10 Blazer, 6.2 performance rebuild, 700r4.
    97 VW Jetta TDI, PP520 Nozzles = Fun 2 Drive.
    85 VW Golf 1.6 Diesel, 5 speed.

  20. #20
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    The injectors and lines don't really get "plugged up", in the traditional sense. Debris from a R/R of the lines can contaminate them at the microscopic level, in the internal passages and valves.

    I agree with your supposition, though. If it were caused by fuel line contamination, it would likely cause a significant balance issue.

    Have you physically removed the PPE, yet?
    1985 Blazer 6.2
    2001 GMC 2500HD D/A
    dmaxmaverick@thedieselpage.com

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