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Discussion Starter · #1 ·
Hello all, just some background since this is my first post here. I'm generaly a Ford guy but have a friend who has this 2006 LBZ ~200k miles. About two months ago he started having power problems under load and an occasional check engine light. He took it to multiple shops and they balance tested it and said injectors seemed fine though the codes pointed to injectors. He also noticed that when it had problems the coolant temp would drop some.

Finally he got a guy to drive it, check the harnesses and balance test it who said one injector from each side seemed bad but all wiring good. He picked up some remanufacured injectors from Pensacola diesel (I think) and we replaced them. I purchased autoenginuity's gm package to set the injector's calibration setting for the new injectors. After this things seemed good though he did have a check engine light that some suggested he would for a while after changing injectors. This was about a month ago.

Today he called and said he's experiencing low power under load, check engine light and limp mode. I still need to go pull codes but I would guess it's an injector problem again.

What do you guys think? It seems rare to have so many injector problems with an lbz. He's been replacing the fuel filter religiously (more than I would) I think he said every oil change or maybe everyother. I'm stumped and not sure where to go.
 

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Hmmm that is very uncommon for lbz's to have injector problems. Could you give us some more specs on the truck, like is it all stock? Or does it have tuning? If tuning then who's? Does he pull often? Does he ever have to add coolant into the truck? Any blow by in the tail pipe? What color is the exhaust if not black? Also let us know what the codes are, as well as any pending codes that are there. Thanks


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Discussion Starter · #3 ·
The truck is a stock GMC, no tuning, no mods.

He's a piano tuner/repair guy so he does move a few pianos a week in an enclosed trailer but I'd hardly call that heavy duty pulling though it is some. Mostly highway miles sometimes with that load but it is his only vehicle so I'm guessing some short town running will have to be included in there too.

Hasn't mentioned anything about having to add coolant, when we changed the injectors we had to take the upper hose of and so had to add some when we where done with that but nothing abnormal.

I looked at the tailpipes a few times and noticed little if any smoke. He did mention it smoked one or twice but I think it was black and while in limp mode but I don't remember clearly. Here's a quote from a text for the current problem "Lost at least one cylinder east of Morcroft running like a lumber wagon 60 mph hoping to get to Casper. A little smokey yesterday". Still seems to lead to an in injector problem in my mind (maybe a rare warranty exchange, that sure would be nice not to cost him any more).

The codes I had pulled earlier (before the injector change) were injector specific codes though I can't seem to find where I had written them down. I'm suppose to meet up with him tomorrow to pull the current codes so I'll let you know what those are when I get them.

I'm giving him the link to this thread so maybe we will hear from him too for some of those specifics.
 

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Pensacola Diesel is pretty much the worst place to buy injectors from.

What tests were done to determine bad injectors? If the tech just hooked up to it and read the balance rates, that only tells half of the tale.

What are the codes? When was the last time he changed his fuel filter?
 

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Discussion Starter · #5 ·
Ok, just got back from checking out his truck. Guess it was bad enough he decided not to finish the trip but to come home instead.

First thing was no codes could be found (there was some codes in the ABS and wheel sensor section but I'm guessing that was from sliding around on the ice some the past couple weeks).

He did remind me that all we found after the injector change was a glowplug code and it wouldn't go away at that time (that seems to have resolved itself since there were not codes there for it).

I decided to take it for a test drive and before we got out of the garage a P0308 Cylinder 8 Misfire Detected code came up. I cleared and we continued on the test drive never to see it again (BTW, it was running very rough right before I cleared it).

After clearing it we drove for probably about 15 miles while I monitored and cleared codes and variables. The only code that came up, and it was consistent, was P0087 Fuel Rail / System Pressure - Too Low.

I tried running a mapping of the FRP and desired was always higher than actual, it got really bad when the peddle was push hard. My first thought is fuel filter so I quizzed him again on that and he knew the trip he changed it on and found it was September last year (more that the 3 months he thought it was but not outrageous). He's going to change that first then we'll see what happens.
 

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Discussion Starter · #8 ·
Just a quick update. He changed out the fuel filter and it seemed to help but only for a few miles (around 10). Before I was able to get back over there he had taken it to a dealer and traded it off (said he got a good deal). So I guess we'll never know what was going on.

I would have almost bought it just to figure it out. Sorry guys.
 

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:helpl:helpMy truck is having the same trouble and I can not find know one around where I live to tack it to but pulls good but after about ten miles it will go in to limp mod only if I am pulling like my camper around 10, 000 lb. it does not show no cods only egr but I got it by pass no chip stock truck 211k but as long as its not pull something heavy it will run really good I don't know what to do and I really like it so if someone could help I would be thankful
 

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Discussion Starter · #10 ·
Fuel filter is the cheapest, easiest, and most common thing so I'd start there.

It is very similar but his didn't require a towing load to set it off and it always threw some codes. In fact, if it's not throwing codes it's probably not in limp mode because limp mode is caused by a code and will turn on the check engine light. So without a check engine light you have a problem with something that the computer isn't monitoring (maybe low air flow, turbo/intake leak, or bad fuel). I'd check those filters, drain the water separator in the fuel filter (though I think there's a sensor for that), and see if you can get a computer that will monitor codes and sensors while driving (such as autoenginuity or similar).

Sorry I don't have a quick answer for you but maybe someone else does.
 
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