Hi I have a 2000 ford f250 7.3 diesel with 220000 miles on it and just recently I have been having trouble starting it under 70 degrees it starts but run rough have to let it warm up then it is OK. And if I plug it in the block heater it has no problems I could just take right off . Anybody have any thoughts what it could be thanks

It may be caused by the ultra-low sulphur diesel fuel. Many have to add diesel fuel additives now. It may also help to use synthetic diesel engine oil, instead of conventional oil. Engines start easier, perform better, last longer, and get better gas mileage with synthetics.