"Life is not a matter of holding good cards, but of playing a poor hand well." Robert Louis Stevenson

This is my first diesel, can one do a compression test and narrow down the cause?

Good info. The code thrown by Snowball has not reappeared yet, so hoping for more good kms for our daughter!

Misfiring codes for our diesel 450 in my experience is almost always related to intake valves. Sometimes the lifter is seizing or broken (wouldn't be intermittent if broken), other times is worn or burnt intake valves causing compression lost.   Good luck!   Iz

Previously to parking the 05 CDI ( 145K) for the winter, I got the PO302 and about a month later the P0303.  It would fire up on the first pull but run rough (2 cylinders I'm guessing) until it warmed up a bit and as soon as I drove away increasing the RPM (high fuel pressure), it drove as it should for the rest of the day.  But as the temperatures dropped (from 10C, the above example, to 5C and then around 0) it would take 4 pull cycles to keep running, but again once the fuel pressure increased, it would run fine for the day.   I'm leaning toward replacing injector (s).  I was also putting injector cleaner in every other tank, it made no difference.  What should I do when Spring rolls around?