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Discussion Starter #1
Hello. I was hoping to get some Some help or advice with this truck. It’s an 05 with approximately 450,000 km on it. When I first looked at this truck the complaint came in about an engine knock. The first time I scanned it with EFI live the knock was intermittent until The truck got up to operating temperature. Then the owner against all recommendations decided to pull his jet boat to a local river boat launch them back. I heard the knock as he passed me on the road. Since then the knock is present as soon as the truck is started. Sometimes quieter than others. I have checked the balance rates and three injectors on the driver side bank were at -15.0 0MM and the fourth was in the fives but I don’t remember if it was plus or minus. I have swapped out all four injectors on this bank with other injectors and it appears that I get the same result even while moving the injectors to different cylinders. I have done a compression test on the drivers bank and will also do the same on the passenger bank and each cylinder is between 325 and 350 psi. I have done a return rate test off each bank of injectors and Each bank appears to be within spec. Because they were within spec I have not checked each injector individually. I have gone through the wiring to see if there is any chafing or shorts in the typical locations and have not found anything. I have also pulled the Upper valve cover off and checked out the valve train while running. There almost seems to be a vacuum when I pull the oil filler cap off and set it upside down on the fill tube. I will try and post a video that clearly shows how loud the knock is and would be grateful for any advice. I am in and out of Reception area so I apologize in advance if I do not respond right away. Thank you
 

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Discussion Starter #2

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Any injectors that are +/-4 or anywhere near that need to be replaced.
Change out the fuel filter and run a good dose of additive in the tank.
 

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Discussion Starter #4 (Edited)
Thank you for the input. I am completely aware of the balance rate specs as I I am the proud owner of my second 2003 LB7. I will update the profile picture but the one I’m currently driving has 606,000 km on it and still tows either our RV or a utility trailer once a week. That is why I also checked the calculated returns and cylinder pressures on the LLY which is much easier to do than on an LB7. I’ve changed out 8 injectors into these cylinders and get varied but similar results on this bank which still makes me believe either yes one of the other injectors are STILL suspect or the FICM could be suspect or is this something internal? All of the past LLY’s I have been able to shut off a problem cylinder and obviously pinpoint the issue. This truck still seems to have some sort of electrical or fuel or injector issue were shutting off a cylinder does not quiet it but at some point and again originally the noise was intermittent until the engine got warm. Just looking to see if someone has had anything similar or would you send the injectors out to be tested at about $50 CD per injector with knowing that they have the kilometers they have on them or do you throw eight injectors at it at $600 a pop and find out that this is either a wrist pin or a rod bearing. I am not sure of the oil change history but there is no evidence of any shavings or sparkle in the oil. I guess I am unconfident because what a rod bearing or wrist pin start out as intermittent on multiple occasions and then become more prominent? Sorry as an edit to that more prominent would be. First the truck would fire up and run like crap for several minutes which would be obviously an injector/electrical issue and then once warmed up start to knock like the video I provided but currently while starting the noise will be slightly quieter or as today when the temperatures are lower it hammer like crazy.
Thanks Again.
 

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Does a stethoscope help narrow down the noise to a particular cylinder? I would throw in about 4 oz. of TCW-3 two stroke oil into the fuel tank just to see if it quiets down. If it quiets down, the pilot injection events are probably not happening on one or more injectors due to deposits etc.
 
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