Alright I need help. I have got an 05 duramax with 165k miles. Had GM replace all injectors 14 months ago. However the motor has developed a loud knocking noise. When the noise first became present, I stopped at a truck stop and poured in some Lucas injector cleaner. The noise then went away, but after a few days, the noise is back. The noise is very loud at all continuous at all rpm's. The truck has full power and does not smoke, but sounds like a "rod" is out.

I am 1600 miles from home and I took the truck to nearest GM dealer. They apparently investigated and called me back saying it appears that the "rist pin" on cylinder #4 is bad and it will be $11k to fix.

Dealer says injectors tested all ok.

Here is what I struggle with: They say that they believe it is the "rist pin" because when they disconnected the injector on cylinder #4, the knock goes away.

I would think that if it is a "rist pin", that the knock would still be present but maybe not as loud due to no combustion.

Please give me your thoughts before I find myself in a position of getting screwed for $11k and a new long block, when it may be something else.