I have a 955k cat that developed a knock at idle warming up under no load.At first it sounded like a rod knock but was suggested that it made be a bad injecter. I changed all the injecters out with new nozzles and o-rings. It sounds better but still not running on all four after bleeding the lines.I think the cylinder closest to the cab is the one giving problems. The machine has been with me 10 years with no major problems and has just been used on the farm. Any help or procedures to narrow it down would be a great help. Thanks for your support. Dave
Check the valve clearances?
Take a look at the crankcase breather pipe or pull the oil fill cap with it running and see if its puffing from that cylinder, #4 would be the first to scuff if it overheated. Piston slap can sound almost like a rod knock.
I was also thinking piston slap, can sound really close to a rod knock and if goes away as warms would definitely be thinking piston related.