Occasionally my engine rpm will fluctuate while at low speed and no load (20-40mph). When it starts doing this there is much more lag in accelaration when i press pedal. When i turn it off and when the key is turned on the injectors do not buzz/cycle. it will turn over fine but wont start. No smoke so I assume no fuel. I do not see the fluctuation at at higher speed. Two week ago I changed fuel filters with wix, and cycled key on 3 times, took for 12 mile ride and ran fine. That night I drove 1 mile from house, stopped at sign, pressed pedal and nothing, just idled. Parked, turned off and same no start, no injector cycling. CEL came on for first time just before I shut it off. Let set 1 hour and started, drove home. Later retrieved code p0299 with borrowed code reader. Cleared and it has not returned, but it did the fluctuate and no start again. Let it set over night, it cranked and drove home fine. I have read several threads with similar but not all these symptoms. Everything from icp, pigtail, ipr or ficm seem to be possible. Any clues?

07 F350 XL CC 4x4 with 75,000 mi and no mods, that is just used to ride around in, rarely pull or haul and light when I do.

 

p0299 is an underboost code. Could just be a sticking turbo, a gummed up EGR valve or a few other things.

I would test the FICM voltage FIRST. 6.0's, FICM's and Cold Start Problems - PowerStrokeNation

 

Thanks Mdub. I will start on those as soon as I can and let you know how it works out. I've been going thru your posts and others and thought that should probably be done. You have put a lot of good information out and I greatly appreciate the advice.