I have a 03 f-350 6.0, I’ve done so much research and talked to my boss many times (heavy duty mechanic) and we can’t figure out what’s going on so hopefully someone can. This only happens every now and then used to be worse but seemed to get a little better lately I’ll be driving the truck and randomly it will rev up about 500 rpm then go back to normal and do it again etc. Also when parked every now and then it will do random little revs but throwing no codes except gpcm every now and then could that be at fault? I’ve tried many things and looked up many things and I can’t find anyone with the same problem. When problem was bad it would idle really rough with revs and bogging down then be fine for a little then start again when it was really bad lots of black smoke it went away for a while now it’s starting to come back I would just like to get this fixed any comments and suggestions would be greatly appreciated.

 

Is it a/c related.. Have you moved to either all floor or all mid vent to see if issue stops? These are the only settings that don't engage the a/c.

 

no it’s getting cold where I’m from so I haven’t been using ac nor a lot of heat so I ruled ac out I will try that out tomorrow and see if that changes things thanks

 

Yeah but know that even not on "ac" the ac is active. Like mix between floor and middle vent ac is on. Defrost vent ac is on. Mix defrost and floor ac is on.

Only straight floor or straight middle vent is ac compressor off. Not saying this is your issue because 500 rpm rev is not normal but you can easily eliminate ac as a source of the issue by turning it off (not many know that ac works when ac is not selected...)

 

yea I’m starting to think that may play in to it I’m getting it checked at the shop tomorrow thanks for the idea