i have a 1997 f150 4x4 4.6 first i hade code p304 changed plugs , wires. injectors,maf,pcv,and cops.now i get codes p174. checked every vac line no cracks cleaned maf sensor.still have code asked ford mechanic says it might be a burnt valve. doing a compression test this weekend .to see if it is a burnt valve. woundering could a bad egr give the p174 code?

 

Any mods such as a CAI? Any exhaust leaks? Did you use Motorcraft or aftermarket parts?

 

all motorcraft parts no exhaust leaks. every time i swap out a cop i get a different code