04 lb7 knocking issue - Chevy and GMC Duramax Diesel Forum
01-04.5 LB7 Duramax Powertrain Discussion of components that are directly involved in the power production and all that is needed to get and keep the truck moving . Engine , Transmission, Etc.

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post #1 of 3 (permalink) Old 11-25-2019, 11:07 AM Thread Starter
LUPO.LB7's Avatar
Join Date: Nov 2019
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04 lb7 knocking issue

Hi everyone, this is my first post but i have been using the forum for a long time. I have a 2004 chevy LB7 duramax, i just hit 300k and parked it to do the injectors, got all 8 injectors replaced with brand new ones (BDW) including all new fuel lines. went to go start the truck after i put it together and it wouldn’t start, scanner threw out a P0335. took the timing cover off and the reluctor wheel bolts were in the oil pan so i was certain that was the resolution to my stalling issue prior to the injectors. after replacing the reluctor wheel i put the truck back together and got her running, after leaving the drive way there was a really bad knock as i accelerated. I was told that the reluctor ring needed to be timed (with gm pins) if i removed from the oil pump drive gear. i then took it all apart again and put the timing pins in and now that it’s driving again it still has the knock although it is a little better it idles smoother than ever other than the loud knock that comes and goes. i am starting to think it may be an injector as they are not from gm they may have a different spray pattern? but the truck also does not smoke at all.
I was also told that since the injectors are not oem, they may need fine tuning because the truck was bought with a tuner that i cannot remove. my local performance shop is fully booked until mid december and i have been stuck without a vehicle for quite some time.

thanks for any help in advance!
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post #2 of 3 (permalink) Old Yesterday, 07:32 PM
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To narrow down the knock to one injector, you could disable them one at a time with (?).

Your call and would probably involve a fairly sophisticated scan tool which many shops that do diesel work would have.

Maybe someone can suggest a downloadable program for Apple or Android that will get the job done.


2003 GMC Sierra 2500HD SLE ExtCab CA Emissions; 155k; Allison 1000 w/Transynd X2 Flush & Fill; 8' bed; AFE/CAI; MBRP 4" Exhaust; Side Tint, 33% VLT, rear, Limo; Smittybilt Stainless Side Nerf Bars; Sprayed-in Bed Liner; MadJack Fuel Filter Access Door; Regular Used Oil Analysis (latest available on request), Blackstone Labs; EGT/Boost Gauges; Dual Chrome Dipsticks, JC Whitney; Stainless Steel fuel filter head bleeder screw; New WP and Hydroboost; Billet Aluminum Fuel Filter Housing Spacer; Professionally repaired instrument cluster (new steppers and lamps); Does anybody ever read this s%#t?; Injectors under warranty @ 70k; 2nd set DIY @ 155k
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post #3 of 3 (permalink) Old Yesterday, 09:53 PM Thread Starter
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Thanks for the suggestion! Im actually going to have it looked at by a performance shop next Tuesday, my best bet is to trailer it there and have it diagnosed by computer. Not worth the headache of making things worse than they can be. Ill be sure to post an update once its all figured out!
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