I always used to just start my diesel and let it warm for 10 minutes at idle before I drove. Recently I got impatient and started seeing how it does with little warmup time. If I try to give it fuel right after starting it sputters and blows blue smoke about 1200 rpm. With each minute it warms up it will rev a little higher before that happens. It won't rev to 2500 rpm without sputtering until it is completely at normal operating temperature. Also, I drove it at night a couple days ago when it was about 30 out and even at normal temp it would sputter at about 2300. Does it sound like something is wrong? I was thinking maybe I should change the fuel filter to start with...

 

Changing the fuel filter is always a good thing to do especially if you don't know the last time it was done.

Is it using oil?