Help! Cummins N14 knocks at idle but not under Insite cut out test

Hello,

I have 1999 Volvo with Cummins N14 engine.
When it warms up there is intermittent fuel/injector knock, it stops when I put load on the engine.
Also knock goes away when I connect computer with Insite and start Cylinder cut out test mode.
When I unplug injector #2 knock stops and there is normal misfire. Changed injector #2, #4 and #6

No fault light on the dashboard, no codes, changed Engine Position Sensor, no change in fuel mileage, truck pulls fine just this knock at idle when engine is warm.

Been looking on the internet but hardly can find something I didnt try already.

What can it be and why knock stops under Insite cut out test?

Thank you for any info!

 

Anybody?

 

Thanks for replay! Injectors are manufactured injectors from dealer, I heard of bad injectors right out of the box so cant tell for sure they are 100%. I ordered ECM and harness. Will see.

Bad hole or scuffed piston? Shouldnt it knock from the start when engine is cold? It only happens intermittent with warm engine

 

yes, thats correct, when connected to insite and cutout test mode startet but without cutting out injectors yet

 

I read that at when Cutout mode is initiated, ECM sends equal amount of fuel to each injector so all of them could work under same condition for easier misfire diagnosis

In normal working conditions when one injector is overfueling it causes engine RPM to rise, so to prevent it ECM cut outs fuel to some other injector and it causes fuel knock usually on that injector I believe

 

Over fueling is easy to spot using temp gun on cylinders exhaust.