So I have a 2004 f150 3v 5.4 with 135k on it. I have been having the same codes and its been running ****ty with only about 12mpg no matter how I drive. I have been getting misfires and always check the codes, the last codes i got were P0307, P0316, P0174. So now researching this forum and the others i know the first two are the misfire codes and its for cylinder 7. I had a misfire in 8 than 4 now 7 is it possible that the engine is just finding the weakest coil? Now the P0174 obviously bank 2 lean condition. When i first got the truck I had trouble with the IWE system and I was told to blow air through the vacuum lines after disconnecting them. When I did that I heard a pop and got worried but everything seemed to work after. Well for months I have had the lean code and I am thinking that maybe I blew one of the vacuum lines behind the MAF causing the code. Are the vac lines somehow connected? Is it possible to have done that or am I over thinking this?

 

You likely have a vacuum leak.

 

Alternating cylinder misfire makes me think you are having an issue with the camshaft and/or crankshaft position sensors.

 

That sounds about right I do have a code for the camshaft sensors. We found that the vacuum resivour behind the battery was blown open and a one way valve not working so fixed both of thiosw but still have the misfire. I will take a look Into what was suggested see iif that's the case since these coils are not that old