I have fought this same problem for almost 2 years now. My F150 will frequently intermittently "buck and jerk"/hesitate/stutter and always throws a code for a lean condition on engine bank 1...as well as sometimes showing a cylinder specific misfire or just a general misfire detected within so many revolutions after start-up code. Rough idle and when it acts up while driving the RPM's will fluctuate wildly...first dropping drastically and then it will gain RPM, then drop again, then gain, and so on. Generally if I let of of the gas for a few seconds I can find an RPM that it will not fluctuate from by itself until I get home. I have replaced all spark plugs (some more than once), pcv valve and hoses, intake gasket, and all 8 fuel injectors (some more than once...thank goodness for a warranty on them). I have had the fuel pump tested with a pressure gauge and it seemed fine. Coil packs tested and appear to all be fine on cylinders that show a misfire. My problems have occurred at all RPM ranges from idle to over 3,000...but most frequently occur around 1,500 to 2,000 RPM while on the highway running roughly 55 or so mph. Seems to get worse the longer I drive it at one time and/or the warmer the engine temp and outside air temps are. If I drive long enough after this begins to occur it sometimes will not allow me to run more than 30mph or less as the max rpms with out problem decrease. It eventually can get to the point that it seems that it wants to die. To me it seems very similar to the reaction of a riding lawn mower engine when you pull the choke...just usually at 55 or 60 mph haha. These problems also do not occur everyday...it was 87 degrees on my way home from work today and the truck ran like a dream but acted up yesterday when it was somewhat cooler high 70's or so. I have had it to several Ford dealerships for maintenance as well as individual mechanics and no one has solved the problem yet. This is driving me crazy! Any help/suggestions are greatly appreciated.

 

Also no diagnostics that have been ran on the truck do not show that the MAF sensor is bad nor an O2 sensor. But at this point I don't think there aren't many other causes left that I know of. I did one time on a code readout from autozone get a possible cause of a failing crankshft sensor...along with several other listed possibilities. But I haven't talked to anyone that thinks its a crankshaft sensor yet. Also I forgot to include that my truck has a little over 89,000 miles on it currently if anyone would find that information useful.

 

Have you had the cats tested? Clogged cats with keep the engine bogging once they load up with excessive gas.

Lean means the truck is adding fuel and still can't get the mixture right. Have you tested for vaccuum leaks?

 

Yes. I had it vacuum tested at a Ford dealer when the problem first arose and that is when the pcv valve and hoses were replaced. It was also vacuum tested again more recently a year ago at another Ford dealer and there were no leaks present that they found...they also flow tested it at that time as well. Upon doing the flow test they discovered several injectors were diagnosed as failing/bad and the rest were no better than marginal. So I just went ahead and had then replace all 8 injectors.

I have not tested the cats though. I figured that if the cats clogged the problems would be more frequent as in everyday. Whereas the problem may occur everyday for a week then everything will run fine for 2 days, then the problem comes back. I actually made it from about July of last year to the beginning of September last year without any trouble. Then all of a sudden the problem was back. Last service before last July was that previous May when the injectors were replaced.

I recently had the injector (under warranty) and plug replaced on cylinder #3 because it showed a misfire.