Fuel Rail pressure.
 

OK so i get up this morning and its about 20 degree out side go to start my work car and nothing but sputters. So i decided better get the diesel started, Haven't had it plugged in and it hasn't been started in about 4 days. Starts fine but when it does it is a rough idle and races up and down for awhile. While driving to work my dash mount (Spartan tuner) keeps flashing frp warning signs being to low. The truck is running realy rough and wont stay at steady speed but still has plenty of power. On the way home from work this afternoon i tripped a engine code that read fuel rail pressure low. Any one know what might be a cause or a fix. Hoping its nothing major, my thoughts were with ice in the lines or in the filter, but that should have melted today as it got warmer. I haven't drained the water fuel seperator since ive had the truck, but ive only had it 3 months. any insight would be greatly appreciated.

For those who may also run into this problem i took it to the ford dealer where i bought it turns out it has a bad fuel rail pressure sensor and also is needing a new engine wiring harness..... thank god for that extended warranty....

I would have never guessed those things. My initial guess would have been fuel filters gelled in the cold and it was just not supplying enough low pressure to feed the HPFP. Thanks for the udpate! :c: