Diesel acting strangely

I've been searching archives for some thing simalar to my problem with no success. First this is a 1550, indirect injection diesel and this problem has just started recently say over the last 2-3 wks progressively becoming worse. I park it in a heated shop, temp kept just about 5 degrees above 0 . When I first start it and it starts easily with about 10 sec preheat, it smokes alot with white to blueish coulor and is unresponsive to throtle, won't rev up. After I start it I move it out of shop and allow to warm up, as it warms up I will be able to increase revs but when I do there is a knock I hear in engine, no knock I can hear if left at low revs say 1000 RPM As It warms more I can increase revs say to 1500 with out hearing knock. After running say 20 min to half hour smoking has cleared up and can increase revs to 1900 to 2000 with out hearing knock. Haven't done any investigating at this point. Seems to me to be a fuel problem either pump or injectors, possibley valves. From archives figuring to go out pull exhaust manifold and see which cylinder(s) are smoking when its cold. May have to wait for it to cool as just finished feeding. Any other sugjestion as to where to start looking would be apprieciated as I use this tractor every day for feeding and can't aford for it to go down completely. Thanks Rocko.

instead of pulling the manifold i use on of those themomiter guns with lazor lite harborfreight sells them for 35 dollars works good for me

You can also squirt water on the manifold ports to find a dead cylinder. Those firing will cook the water right off, the dead cylinder will have the water just sit there.

Check the valves might need ajusting or stuck.When only one or two cylinders are fireing they get so much fuel at a slow speed they hit hard and sound like a knock,get the others fireing and the knock will disappear.Might have one bad injector fouling up a cylinder and energycell plus those valves.