04 F150 5.4L 3V Screw
160,000 mi

Hey guys sure need some help here. Well my issue is as the title says, I have got the p0012 error code. I can clear it on my Evo and then the VCAM starts reading again for awhile then stops and only reads zero. I did an oil change to Mystic 15 50 oil (dumb idea just a true believer in the oil) and ran about 200 miles. Have now switched back to MC 5w 20 and replaced the VCT solenoid. No change. I do not hear anything strange out of the phasers or timing chain. Typical rough idle but doesnt start hard or anything. Can coil packs, plugs, or cam position sensor cause this. Are there honest diagnostics that the dealer can do for, or are they gonna just throw parts at? I am not affraid of doing the phasers myself, I'm very capable of that, but I would like to narrow it down and trouble shoot it better than I have been able to do. Probably a crap description here and let me know what other info would be helpfull.

Thanks a bunch in advance.