Rough idle? P0171, P0174? Here's what you need to check first!!!

[Lightnig]

Yay, finally got this accomplished. Thanks for the heads up on the hose.

I had no end of grief getting this done myself, mostly just finding the ends of that bloody hose.

For those of you that may be having difficulty locating both ends of the hose:


The top right is on the back of the Throttle Body underneath the cowl against the firewall. My fat hand had to go over top of the hose, it simply would not go under.

The bottom left is the PCV itself, where it is inserted into the Right (passenger) side valve cover.

A close up of each end:


My hose did not come apart in one piece. The hose on the back side ripped (it was still soft and flexible), and the tube came apart in 4 pieces - one piece out of the 90 disappeared entirely. Good thing darn thing that I had the replacement on hand.

By the way, the one my dealership sold me was labelled F75Z-6C324-JA and fit properly.




Definitely smoothed out the idle, and no more P0171 or P0174 codes yet. I guess I will know later this week if this solved the problem in the long run.

 

[peterbs]

p0171 p0174 PCV 90 elbow deformed w/ hole

I had both codes p0171 and p0174 on my 99 expedition 5.4 liter. Cleaned my MAF, but codes came on again. Ordered the non heated PCV hose, not realizing I had the one with a Y right off the PCV valve. I should have listened for the noise first and diagnosed by leaving the engine running and wiggling the hose around. If I had, I would have found the obvious huge hole on the inside of the 90 elbow attached to the PCV valve. Went to autoz##e and bought a $6 PCV elbow, 30 seconds later I was done. I little bit of wigglin hoses would have saved me the expense of buying the part I didn't need (look for it on ebay). If you have these codes, rule out hte obvious easy repairs first,......locate your PCV valve, start your engine and feel around for a leak, depending on it's size, wiggle the 90 elbow hooked on to the PCV, if it's bad you will will hear an obvious change in the hissing sound. I cleared the codes and because of the extremely poor condition of the elbow,that I fixed it. I will uprate if the codes come back on.

 

[scottsbro23]

Yay, finally got this accomplished. Thanks for the heads up on the hose.

I had no end of grief getting this done myself, mostly just finding the ends of that bloody hose.

For those of you that may be having difficulty locating both ends of the hose:


The top right is on the back of the Throttle Body underneath the cowl against the firewall. My fat hand had to go over top of the hose, it simply would not go under.

The bottom left is the PCV itself, where it is inserted into the Right (passenger) side valve cover.

A close up of each end:


My hose did not come apart in one piece. The hose on the back side ripped (it was still soft and flexible), and the tube came apart in 4 pieces - one piece out of the 90 disappeared entirely. Good thing darn thing that I had the replacement on hand.

By the way, the one my dealership sold me was labelled F75Z-6C324-JA and fit properly.




Definitely smoothed out the idle, and no more P0171 or P0174 codes yet. I guess I will know later this week if this solved the problem in the long run.

My wifes 03 Eddie B (5.4) was having the same issues but no codes. I removed the same hose as above. Except it is different, starts and ends at the same spots but has a "Y" in the middle that plugs into the side of the manifold port that has coolant lines running thru the port as well. Hose portion tore in half when I was removing it from the port. The 90 deg. elbow was deteriorated and had a crack. Auto parts store said it was a Ford Factory part (complete hose assy)..hell with that, bought an elbow and cut a section of tube to replace the split section. Then removed and cleaned the Throttle body and IAC. Went to buy the gaskets for IAC and Throttle body, computer does not show the correct throttle body gasket for the 03 5.4L. I Installed a throttle body spacer on my sons 99 4.6L a couple weeks ago...and the gaskets are the same for both. Ford claims they stopped using this gasket in 2001. NOPE... So if you do this ask for a 99' 4.6 or 5.4 throttle body gasket. She purrs like a kitten now...(gotta unplug the neg on the battery as stated in previous posts)

 

[kgreenjinx]

You guys Rock!!! I have been chasing this CEL for quite some time. getting a 171 code and that's all. 2003 expy with 5.4. As scotts bro said 03 is slightly different than what has been posted on here but same place. Felt around the hose and slowly moved it and heard a huge hiss. The lines Y off and there is a straight rubber nipple that is leaking on mine. No hissing unless you move it. You guys are a god send. Hopefully get mileage back up to 15. Now off to the auto parts store to find a replacement "boot" I need to go to town anyways to get a 30mm, 21mm and 19mm impact sockets for air coil conversion, 3.5/2.5 spacer lift this weekend. Have it tore somewhat apart so hopefully can post some pictures.

 

[sonofalver]

this post saved my butt. 6.99 rubber boot was the fix

 

[Berg]

same 2 codes everybody is mentioning. mine had the boot melted closed ! trying to get it off it broke and half is off and half is sill on. it seems as if its glued on or something !!!!! im attempting to get it off piece by piece but its very tight back there. truck out of commission for 4 days now.i get off work its almost dark

 

[Berg]

def was the elbow.changed it and no more codes and smooth idle.wife drove it and said it felt like it had more power runs with less noise.keep in mind she never knew the truck was out of commision or had a issue...im guessing since mine was melted closed it was happening over time.i wonder it it was letting in less and less air making everything unbalanced thus creating a rough idle... anybody know if this could have been true?

well she runs good as new.i did clean out the MAF like 3 times before I found out it was a issue with the elbow.maybe that helped too.

 

[glen615]

Hi All

I hope I a can get a little help on what my issue with my 2001 Expedition might be. This is 5.4 V8 2x4. The check engine is on and throwing P0171 and P0174 codes. Both banks I understand from my research. So I have replaced the PCV (the whole assembly, hose, and elbow) since it came together from the dealer. I also replaced the plugs with motorcraft plugs and also replaced all coils and boots. One of the hardest automotive repairs I've ever done). I have also cleaned the MAF, and IAC, as well as replaced the IAC gasket.
So I think the initial troubleshooting can be considered completed. So why am I still getting the damned codes?? I'm at a lost, none of the coil cables seemed melted or otherwise damaged and I can't think of where else to check. I'm hoping the you guys might have some insight

Thank you very much in advance

 

[hwy73]

I believe those codes have to be cleared after the repairs are made. Either with a code reader plugged into the OBDII port or by disconnecting the battery for a period of time to clear the computers memory.

 

[glen615]

I had cleared my codes when I completed the work and the truck seemed to run smoothly but about 80 miles later it wanted stall. It tends to happend when slowly accelerating from a stop.

 

[Berg]

did the part you bought have new elbows on both sides of it? the elbow on the end that connects by the throttle body on mine was melted closed.now its runs like a dream and even sounds different too

 

[glen615]

Yes the hose came with both elbows and the pcv.

Yesterday I replaced the MAS with a new one and that did nothing and I also replaced the fuel filter but no luck either. Tomorrow I will swap both upstream 02 sensors and possibly the fuel pressure regulator and after that I have no idea what else can be generatoring both P0171 & P0174 codes.

Also, yesterday I fed smoke through the brake booster line from a fog machine hoping to see it leak somewhere but it seemed airtight everywhere even checked under the car. I put s good amount of smoke in too

Taking a break today for the holiday but back at it again tomorrow. Have a happy thanksgiving!

 

[Berg]

sux !

 

[glen615]

Well it turns out it was the fuel pump. Just goes to show that the lean codes
generally associated with a vacuum leak can sometimes be a more involved. Fortunately I found a guy to drop the tank and replace it with all for under $450.

I returned the o2 sensors & fuel pressure regulator. I hope my experience helps someone.
Thanks for the input!!!

 

[Lane24]

Glad you found your problem !!! Like the title says , these vacuum leaks and simple things are what you need to check first before you let someone talk you into spending the $$$$$$... and a good percentage of the time that's all the problem is....but unfortunatley, sometimes the problem goes a little deeper. Thanks for sharing your experience in this thread. It's going to help someone for sure.

 

[ohillny]

Life and financial savers

I have exact same symptoms down to the whistling and being that it is -3 and -22 wind chill here in rochester the EX would not get me were I needed to be this morning thanks for this post I am sure this is my problem as I have the same codes and check engine light on since replacing my coils and plugs probably damaged that hose then.. Once again thanks for this post!!

Very common symptoms we all have at one time or another with our 5.4L is a rough idle where we will have high idle for a few seconds when slowing or coming to a stop followed by a drop off to a very low rough idle after stopped for a few seconds sometimes even to the point of stalling out.

I had this problem for a few weeks, and then the weather turned cold, and it got even worse to the point that my ‘ check engine light’ was even coming on. I took it to the dealer, and they replaced my IAC. No change. Still idled rough. Still had the CEL. The only change was the weight of my wallet!! So I turned to the internet!!!

By doing some ( a lot) of research on the subject from other Ford sites and forums, this is a culmination of what I’ve found out. The fix is a little rubber ’boot’ or elbow with a crack or a hole in it causing a vacuum leak.

The Ford dealer will run a diagnostic and indicate that it returned an error code P0171 and P0174, which indicates the engine is running lean. They will most likely recommended the following service:
Replace EGR valve - Replace PCV valve - Replace differential feedback EGR sensor -Replace mass airflow sensor -clean fuel injectors
all at a cost of almost $800. Yikes!!!!

The first thing to check is your vacuum assembly. You most likely have crack or hole in the little rubber elbow that connects to the intake from the PCV valve on the right hand side of engine. Even the slightest crack will allow more air to be sucked into the engine causing a too lean mixture.

The PCV valve is in the right valve cover... which is on the left side when your facing the engine (passenger side). It's under a lot of other hoses so it is very hard to see.. The hose goes back from the valve, then toward the drivers side to attach to the back of the intake way back between the engine and the firewall very close to the top of the engine. The common faulty part is the rubber boot that connects the hose to the back of the intake.

The way I found it was to follow the hose back from the valve cover. I sat right on the engine shroud, and felt for the tube sticking out of the top rear of the valve cover on the passenger side of the engine. With the engine off, it pretty much just pulled out and went back in real easy. Then I just followed it with my hand the best I could ( with the motor now running so be careful!!) until I got back to the firewall, and it actually comes up from underneath the rear of the intake. . You can kinda reach your finger up under there to where it's connected, and feel and hear a definate shoosh sound when your finger goes over the hole or crack in the elbow.. You can't see it, but you can definatley trace it back by following that tube. You'll know it when you find it because your finger will plug the hole, and your truck will start running smooth again!!!

The part number for the entire vacuum assembly with the correct boot on it is - F85Z-6C324-AA probably around $30 -$40. Or you might be able to just replace the elbow itself. Either way, make sure if you do have the leak, to make sure you have the replacement part handy before you take off the old one, because it will crumble in your fingers!!

Hopefully you just saved a few $100, and a lot of frustration. I know I was pretty happy when I found this easy fix!! Good luck!!!

 

[ohillny]

she is stalling again

I replaced pcv and hose to the back of the intake was running a lil better clean MAF sensor still the same idle. Temp dropped last night this morning she was running real rough. I also was going to change the fuel vapor separator tube this is the one that goes to the brake booster. I don't think this is the problem but it kind of worn out also. Still I am at a lost any other suggestions? should I give the TB and that whole area a good cleaning? Suggestions are greatly welcomed..

 

[bedrck46]

You may want to clean the exhaust ports in the TB which involves removing the TB

also would suggest new plugs,cop's, etc

 

[ohillny]

THanks

Yeah gonna have to get in depth with it, seemed like I started having these problems after replacing all my plugs and coils honestly.. THanks again for the suggestions..

 

[bryanaceron]

Yeah gonna have to get in depth with it, seemed like I started having these problems after replacing all my plugs and coils honestly.. THanks again for the suggestions..

had the same problems did the same replacing all the parts and come to find out the new set of spark plugs were defected. now runs like a champ