Need help with A 2004 F150 5.4 3v Dreaded codes P0171 , P0174 , P0420 and occasionally P0300
New seal on air filter
Good voltage at the MAF 0.00 and cleaned anyway
Long and short trim are really low nothing close to 13 added together No Vacume leak detected
I am at A loss HELP
I know I am missing something

 

Those aren’t anywhere near as dreaded for a 3V as they could be.

Check fuel pressure, but there’s a good chance of a vacuum leak behind the MAF causing those lean codes.

I know the 2V Tritons had an intake elbow facing the firewall that rips open. Not sure if the 3V engines still had it.

The 420 is for cat efficiency and that makes sense depending on how long that misfire code has been around.

 

I just had the engine out to Replace all the Chains , Guides Phasers , Tensioners , Cam followers Lifters The works all Ford parts
While out I replaced the Power Brake booster connection hose Checked the main Vacuum supply fitting it was still good and tight .
Checked the Injectors and Manifold for leaks found none

 

Attached is a list of possible causes from Ford PCED for P0171 (also applies to P0174).
PCED is just a big thick book for powertrain control diagnostics Stands for Powertrain Control Emissions Diagnosis

 

Even though I recently replaced the Mass air flow sensor like 1 1/2 yr ago It looks like it is the culprit
Lett you know if it clears all the drive cycles and passes emissions here in The ARMPIT of America
AKA Portland Ore