LB7: Loss of power!

[Stevenmc89]

Well guys I'm swapping forums from another one to here looking for some help. I have a 2002 lb7 that's lost half its power. I have 3 week old injectors, new fuel filter, 6 month old cp3 and no codes. I've also cleaned MAF and map sensors. I'm completely stumped. Took it to the dealer and said everything looks good supposedly from the tec II. I rebuilt the fuel filter head and replaced the rubber lines hoping it was just sucking some air but it didn't help. I honestly believe its not getting enough fuel due to the fact it used to blow black smoke easily and now it has none unless I completely floor it from a dead stop. I heard y'all are the best of the best here so I have faith y'all can help me! Thanks everyone for helping the new guy in advance!

 

[THEFERMANATOR]

Did it lose power with the injectors? If so you probably had worn out nozzles or leaking valves causing your old ones to dump diesel in whereas the new injectors are actually metering it correctly. I did an LB7 before that was 100% stock, but would roll the coal like no tommorrow. Put new inejctors in it and it ran like new again(but it was down on power a bit from before due to the injectors now flowing what they should be). Also it would be a good idea to get it on a tech 2 or EFILIVE to log rail pressure, pulsewidth, and commanded MM3 of fuel to see if it is going to full throttle or not. just because you have new injectors doesn't mean you didn't get a bad one that could be causing issues.

 

[Stevenmc89]

It started running like crap before the injectors. I checked the balance rates one day and saw a couple out of spec and assumed it was the problem and paid the local dealer 3800 to put 8 Bosch remans in and nothing changed. It's so bad it loses speed pulling hills on anything but my 120 tune and it sounds like I'm pulling a mobile home behind it it's straining so bad. Plus the predator says 30-40% engine load in park idling and around 70% in fifth just cruising at 55 on level ground. One thing I have noticed is my coolant fan is always on but I doubt with it being engaged would cause it to strain that bad but I'm no expert. Also just wanted to say I've seen a lot of your post and wish I had half the knowledge of the DMAX and allison that you do!!!

 

[THEFERMANATOR]

The engine load isn't a good indication, need to know what it is commanding for Mm3 of fuel. At WOT on a stock tune it should go to 89MM3 of fuel over 2200 or so. Also check rail pressure and make sure it is holding close to commanded. Not sure if teh DIABLO will show you these PIDs or not. It may be worthwhile to post up and see if you can find somebody with EFILIVE to take a look at it as it wouldn't take long to do some basic logs to see what is going on.

 

[bigjohn]

You still haveing problems with your truck. And your cp3 pump is not that old did you have that checked it could be weak . Or look at the rubber hose from the fuel filter houseing to the ficm might have cracks could be your problem. These guys are knowledgeable on this site.

 

[Stevenmc89]

I've done replaced the rubber hoses. I did get a glance at the tec II when he had it hooked up and noticed the actual vs desired was not 100% dead on but it wasn't off by much. Maybe 100-200 psi at idle. I can read the fuel rate in mm3 and desired in psi but not actual pressure so I'm screwed on that without getting a tec II or solus

 

[Stevenmc89]

The highest I could get was 74.1 mm3 on the 120 tune

 

[THEFERMANATOR]

Sounds like your being fuel limited, most likely a bad MAF sensor or an air leak in it somewhere. Check the resonator at the turbo to see if it is cracked. teher has been a few of those plastic resonators crack and let air in which is air teh MAF doesn't measure and it throws the airflow readings low which limits fueling. Going to have to dig into it and see if it is airflow, throttle pedal, or what limiting it as I would think DIABLO would at least set the fueling to go to the stock 89MM3 of fuel displayed.

 

[dracing70]

I've been having this prob. For years with my lb7. However it is not severe enough for me to have dug way into it. It still gets great mileage is I have left it alone. But one day out of no where the truck stopped performing like it used to. The first tell was just as u Said. It used to role coal. Then one day it quit. Now it will only do it if stomped on from a start on Big tune. Injectors were tested and even replaced cp3 tested replaced. It just seems to lack fuel. Rail pressures r good. I even replaced the maf and nothing. The only large negative affect I noticed is out of no were it will lose power at about 98 miles an hour. And it's not the tune cause it has efi and all limiters r removed. It's very strange. I'm convinced it is either the turbo or factory fuel lines restricting. Everything else has been changed. Like I said its a grocery getter so I have not really worried about it. I beat my head against the tool bench for about 6 months with no success changing out parts. Let me know if u figure it out.

 

[Stevenmc89]

Definately not the news I wanted to hear. I've gotten to the point where I'm seriously about to trade it. I hate to because it took me 3 years of begging the man to sell me the truck and trying to get a loan etc because it was a great truck but 3 months after I get her it goes to crap. I've read one post about someone with the same problem but it turned out his was the ECM and if I find one at a good price I'm gonna try that. I've been trying my best to find a tecII or something of the like to monitor my truck without any luck

 

[Stevenmc89]

So I have an edge cs now and can watch rail pressures and all that other good stuff. Anyone feel like helping me diagnose it now? Anyone know what parameters i should be looking at that could cause restricted fuel?

 

[THEFERMANATOR]

Rail pressure(desired and actual), MM3 of fuel commanded, and pulsewidth for starters. Once you have those it will give an idea of what it is doing. If any look off then next you want to watch boost, MAF, and timing.

 

[Stevenmc89]

As always, you're the man and thanks alot! I'll check out everything and report back to you tomorrow and hopefully get this thing figured out.

 

[Stevenmc89]

I can read calculated fuel rate, main injection command, main injection fuel rate, main injection timing, pilot injection command, pilot injection fuel rate, and pilot injection timing. Would any of these be the pulse width? Unless I'm missing something I don't think I can read the pulse width. Note the edge just says inj so injection may mean injector

 

[ooeddym]

Did you ever figure out the loss of power problem?

 

[Santos_LBZ]

Has anyone found a solution to this. I have a 2006 LBZ with EFI Live, modified exhaust no cat. On a cold day it will drive for like a mile then lose all power and just start pouring out black smoke. An it will be like this for about an 1/8 of an mile. Then it will clear up and not come back till next cold start up. I've changed the fuel filter, cleaned the Map sensor, changed the oil, and have gone through tanks of diesel. I've heard possibly injectors, tuning, and egr but none for sure. It drive fine after that though. I've put the tuning on stock but still does it. The boost PSI is at 1 when it happens so could it be boost related

 

[Dmax0372]

03 duramax

I have a 03 duramax and I have spent a ton of money trying to fix it so far I have had a new turbo new egr cooler new banks big head waste gate new injectors new glow plugs and haf it a numerous shop and they have said ballance rates are great .my problem is it seens to run good with no trailer but when I try to tow my 22 foot toy box and I hit a hill it losees all power and I have the peadle to the floor a 3 hundred rpm and it will only do 55 mph please help I have already dropped 5 g on trying to fix it thanks