Started missing and knocking like it had a bad injector
Scanned it and found injector codes. No ficm code. Did a cutout on all injectors and couldn't communicate with 2,4,6 and 8 so I thought it was the wiring harness.
Checked harness, checked ficm voltage, cleared codes and still came back with number four
Low voltage. Pulled 2,4,6 and 8 injectors checked all prongs and seals
(Replaced number four) put everything back together and started truck
Still had a bad miss and no power.
Done a Relative compression test and cylinders four and five were low. Pulled the new #4 injector back out and pulled number five out. When I pulled the stand pipe from the right side it had a little rust on it.(looked like rust) when I pulled number 5 injector it looked like it had rust bout mid way of the injector.
For some history on this truck. I've had to change the egr valve, egr cooler, oil cooler and coolant reservoir.