Need a little help in what area to start looking at now. My 04 F150 Heritage has thrown the po171/74 codes. Using the search function I have tried what most people recommended..... Cleaning the Maf with maf cleaner (careful not to touch it) checked for vacuum leaks (checked all the hoses and sprayed break part cleaner all around the intake) found nothing. Where would Be the next best place to start looking? I appreciate the help. Thanks

 

Check the big elbow on the back of the throttle body it has a habit of wearing a hole in it. Spray the back of the TB with cleaner and it should tell you.

 

If both banks are lean, it is most likely the pcv elbow/piping that routes to the back of the intake manifold like said. The best thing is to remove it and inspect it for even the smallest pin hole, most likely on the inside bend of the 90.

 

I appreciate both responses. Where exactly is the PVC piping located. Sorry... I'm sure the answer is quite obvious to most.... I'm just not one of them. Thank you again.

 

It will start in the top of the vavle cover, my 4.6 is on the passenger side about where the number 3 cylinder is. It will hava a hard plastic tube and a rubber hose, it runs around to the back of the throttle body and connects with a rubber elbow. If you have big hands like me it can be a bear to get it off and replaced.. Good luck

 

So I pulled apart the pcv piping from where it goes into the side of the throttle body down to the valve cover and it looks perfect. With it out I blocked one end with my thumb and blew through the other end ( I know not very measurable) and it didn't seem to be leaking. reinstalled it and with the truck running sprayed it with brake part cleaner and nothing happens. The only area it seems I may get a response from ( and I say may because if it is revving up using the spray it is almost unnoticeable) is below the throttle body. It doesn't rev up if I spray the throttle body itself, but directly below it seems to cause the idle to go up some, I think.

 

The PCV routs to the rear as well. Back of the TB, by the firewall. The side hose is nothing more than heat transfer. Pcv flow runs to the back. You can't just do half the job, you need to test the entire PCV system. Stop spraying that crap all over the engine as well. You going to end up making more problems.. Do it right.

Tons of info and pics thru search. TONS. This question use to be asked every other day lol.

 

I'm gonna take a whack at this, is this a 4.2 V-6 or is it an 8 cylinder?

The info so far seems to relate to those codes and fixes for the 4.6 or 5.4. The reason I ask is the 4.2 the PCV does go into the side of the throttle body and the V-8's go into the rear. I didn't see where the OP posted his motor.

This sounds like the classic 4.2 isolator bolt issue. But I could be completely stupid (please hold comments) as I thought the Herritage could come with the 4.2.

If the OP would post his motor it would help alot.

 

I apologize.... You are correct it is the 4.2 v6. Thank you

 

It pays to ask questions in the correct forums. Your way off, in more ways than one lol.

 

If you're referring to the year of the truck.....isn't the 04 heritage model just an 03 body style released in 04 until they came out with the newer 04 body style? Please Correct me if I'm wrong. And if this is not what you're referring to please don't be so cryptic and enlighten me. Thank. You.

 

- Are you kidding me ? You can't teach common sense, - it doesn't stick.

Yea, you did say Heritage. No, that's not what I'm referring to.

I'm not going to tell to start ANOTHER thread somewhere else (the correct place) without you asking a moderator to delete this one first.

Hint, - jgger probably nailed it. Specially if you checked all the hoses thoroughly.

 

You've been unbelievably helpful . I certainly hope your not an indication of what members on this forum are like. To those individuals that responded with out being a pompous ***.....I truly appreciate it.

 

Thanks for the compliments. But hey, maybe next time you'll post in right forum. That would much more of an asset, which in-turn, would only benefit yourself. Like what you learn, but most of all, focus on understanding it vs whining about how you got there.

 

And maybe next time you'll simply point someone in the right direction and not waste people's time trying to "be about something" on the internet.