Hey everyone! I'm new here so let me start out with saying thanks to everyone for helping out. I've got a 99 f350 powerstroke. I've had it for 6+ years. I've got 310,000 miles on it. Oh let me add it was manufactured in March of 98. Only mods I've done is a cold air intake and a chip. (Dont remember who makes it) it's always ran great with zero issues until recently. I'm mechanically inclined with gas engines and have been learning little by little with diesel. So recently it started running rough. At idle and taking off from a stop. Once the turbo is spooled it seems not have any issues. The rough idle is almost like it's missing. This morning however I noticed something. I have a remote start on it. I started it remotely this morning and it was idling smooth. Once I put the key in the ignition and turned the key to run it instantly started idling rough. I no this truck has had issues with blowing certain fuses before I bought it. I climb cell towers and purchased this truck from a tower company I used to work for. When it was a tower truck it was under a tower one day and drove there fine. However when it was time to leave it wouldnt start. We had to tow it away from the tower in order for it to start and it's never happened again since
(10+ years ago). I dont no if that info was needed just thought I'd through it in. Anyway any help would be greatly appreciated as I really dont want to pay a dealership. Thanks again

 

Try starting it in neutral instead of park and see if you still have rough idle. If it idles smooth when started in N then move the gear lever to park and if it is still a smooth idle you have a bad neutral switch on the side of the transmission, and that is about $45 part. Let me know if this works or not. I guess I am assuming it is an automatic, but I suppose it could still be this similar part for a manual trans.