i replaced the plenem gaskets, bolts, and sutch. and it fixed my code back when i had around 75 on her, now at 108 and hasnt came up again. check this first the kits from the dealer, and it cost 100 and up. but the f150 have a big problem with these gaskets. not all will be it though so this is not a fix for everyone. i spent 500 dollars trying to get rid of that code, but inspection was out, and it failed and i got pulled over twice.

 

Just wanted to let you know that I had the P0171 and P0174 codes on a 1995Grand Marquis 4.6 and your writeup and especially the pictures gave me the hint as to where to look. I found the hose (with almost identical damage) in about a minute with you help. I would not have thought to look "way in there" for quite a while on my own. I had already checked the PCV hose and valve on the valve cover end before I read your post. Thank you very much for taking the trouble to post that information - sorry I don't have an F150.
If I could add anything that might help others - when you lift the PCV hose/PCV valve out of the valve cover on a 4.6 the damaged elbow gives it a "limp" feel (not springy). I put a 2" x 2" aluminum "heat shield" (friction fit)under my new piece of heater hose to deflect the engine heat.

 

glad my post has been some help to some. since then i've had the same problem a couple of times and fixed it the same way, had to replace the dpfe? (little box with 2 houses behind the alternator) sensor once. last time i changed those hoses from the back of the engine i found some longer pieces of hose and ran that out towards the firewall and over closer to the wheel well and use the splitter piece there and went back towards the egr area. taking out some of the harder curves/corners has seems to make the hoses last longer.

 

Just woke up, what year is it?

 

The codes on my 01 5.4 were caused by a cracked manifold. I replaced all of teh OPCV line, EGR, and AIV first before finally replacing the intake.

 

Swine70tx,

My neighbor helped me troubleshoot the same hose as yours on my 99 F-150 V6 a few months ago (just rolled over 224,000 miles yesterday). The hose was so dry rotted it fell apart in his hands. Replaced it and everything was good for about a month and then the same P0171 & P0174 codes returned.

But now I heard a vac leak at the front of the engine. Looked at all the obvious hoses and just spent this afternoon finding the hose hidden under the intake manifold directly under the idle control.


Once you get the air intake out of the way and remove the plastic cover resting over the throttle body and that protects the throttle springs, remove the vacuum hose that goes to the brake booster (mine was also getting pretty brittle, so I removed it entirely and replaced it as well. HINT: At the brake vac booster it has a nylon clip that slips onto the nipple and you have to squeeze the tabs to get it to slide off).



The small hose that was leaking was on the nipple that hangs vertically directly under the idle control unit. You can see it here just behind the nipple for the hose that went to the brake vac booster.



On the left side of the engine, it attaches to a hard plastic tube that runs to the back of the engine under the intake manifold. Here it is gently worked into position so the other end of the small hose could be removed.



And here is the hose I'm talking about:



And the hole in it that was causing all the grief:



I replaced it with a piece of vacuum hose since it was Sunday and there was no way to get it from a dealer. I may price it since it has a 90 degree bend in it and was actually pretty easy to get to once I figured out where the hissing was coming from. But the cost of the fix was $4.00 in vac hose (for the 3' I got for the vac booster and trimmed to fit. I used the scrap for the leaking hose pictured above.

 

I have a 2007 F-150 4.6 ... took it to auto parts to get code on what is wrong with it. code p0174. I see many comments about this code. But none for a 2007. Is it my understanding it most likely the maf sensor? I also have read that you can spray something(forgot what it was) into it and possibly fix it. This is what it is doing, running really rough. Almost like it is misfiring. Is it something that I can fix on my own? Or would it be best to take to my dealership and let them do it. I would prefer the first. I don't want to spend a lot money if I don't have to.

Thanks

 

You most likely have a vacuum leak - although an exhaust leak before the O2 on that side can cause it too. If you don't know what you are looking at it would be best to take it to a shop.

 

Ok Thank you. We talked to a mechanic. He also said it sounded like a vacuum leak. We are suppose to take it to him one day this week. So he can know for sure.

 

When looking for the 90 degree rubber elbow on my 1998 5.4, I've had success using a 90 degree boot off of a spark plug wire. One side is 3/8" the other is 5/8". It stands up to high heat and is free if you have an old set of wires around!!!

 

A tip for chasing down vacuum leaks is to start the engine and while it is idling spray carb cleaner or autozone(only brand that seems to really work) brake cleaner around the various hoses. Use the small straw and lightly spray each line and manifold areas. When you spray the cleaner near the leak, the engine will increase rpm slightly which makes it 100 times easier to locate. It should only take a couple minutes to pinpoint this way. NOTE: DO NOT ALLOW THE ENGINE TO WARM UP COMPLETELY AS THESE CHEMICALS DO POSE FIRE HAZARD.

 

Usually, the computer is too fast to compensate and you'll never hear anything change.

Use a scan tool monitoring either the upstream O2 voltages or the short-term fuel trims and you now have a valid diagnostic method.

 

Not to be lame or anything, but i am super desperate and cannot find information on what I am looking for. I found the elbow, and it was just flaccid and lame, and in need of replace. I know that it's on the back of the intake, but does it hook up somewhere else, or does the end just stay loose on the intake?

 

The elbow goes between the intake and the pipe that goes to the PCV valve. What year and engine? This thread concerns the 4.2 V6.

 

It's a 1998 f150 4.2
Now I know what connects to the PCV valve. I know the PCV valve went into the valve cover, and it was a Y, with a lose end. So that lose end hooks up with the back of the intake plenum?