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

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ohillny

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omg

That would damn suck if that is the problem as I am sure you are aware that it is not the easiest repair to do. Dang but I might have to suck it up and replace them I thought about the coils to could one of those be bad ahhh I tell its driving me crazy...
 

ohillny

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I am wondering do I have the same problem I both p0174 and 71 this winter I changed intake gasket and a couple hoses. cleared codes. Ran fine up until a month ago got the p0174 code again and it has been giving me trouble starting like its not getting gas. I have fuel pressure. Any thoughts should I try fuel filter first
 

bissbb

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rough idle Lane 24 you called it!

My 04 exped 4.6 was doing exactly as indicated - rpm drop to nearly stall when coming to a stop/idling. The 90 fitting at the top rear near firewall on the pcv line was split. Not the easiest to get to but once removed and replaced appears all is well. I would have been clueless without this being discussed on the forum. Much appreciated!
 

martinek

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I had recently changed both my upstream O2 sensors and the PCV elbow. My truck ran great once again and check engine went out. I now have it running rough, wanting to stall and I get 6 codes, PO136 PO156 PO174 PO171 P1131 and PO1151. I have a 1998 Ford Expedition Eddie Bauer 4X4 5.4L Triton V8. Any and all suggestions would be great.
 

Zombiehunter00

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No such luck on my 2002 expy. I had the 174 and 171 codes and the truck hated the cold weather, shaking and stalling when it came to a stop. As it warmed up the problem seemed to go away- which meant the intake gasket was probably going bad. I replaced the intake manifold and the problems were solved. It seems to be a common issue with the plastic and aluminum manifold ford uses; as I replaced one on my mustang due to a coolant leak as well.
 

TobyU

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No such luck on my 2002 expy. I had the 174 and 171 codes and the truck hated the cold weather, shaking and stalling when it came to a stop. As it warmed up the problem seemed to go away- which meant the intake gasket was probably going bad. I replaced the intake manifold and the problems were solved. It seems to be a common issue with the plastic and aluminum manifold ford uses; as I replaced one on my mustang due to a coolant leak as well.


We have a 2000 that I think needs the intake gaskets too. No leaks in the other common areas. I just drive it when it's about 40. Lol Wife put up with it for 3 winters though. Slight power brake to keep idle up or N. Annoying but worked.
She like a vehicle to function properly more than I do.
If it an get me there and back on 3 tires and a Shinn Fu floor jack....I'm good.
 

Tbaker

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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!!!

SANY1187.jpg

pcvelbow.jpg
 

Tbaker

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Lane I saw a post you had written about the little elbow hose sitting up against the firewall at the back of the motor. It connects the metal PCV hose to a sensor of some sort. Well you were spot on. I couldn't resolve my Check Engine light so I bought the part number you supplied through Galpin Ford in Los Angeles. I was able to pry off the old hose with long nose pliers and a screwdriver and sure enough I had a hole right inside the actual curve of the elbow. Now my problem began there. I could not get the new elbow back onto the part that sits on the manifold. You have to reach far far back with left arm only. I even tried adding some oil to the hose which then made it slippery and I dropped it into the area of no mans land on top of the block. I could not retrieve it so bought the same part again this morning. Do you have any advice for actually getting the new hose back on?

Thanks in Advance
 

1955moose

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Shinn fu, I went to school with his Asian brother Jim Shoe. He was great at sports!

Sent from my N9131 using Tapatalk
 

71Rcode

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i lived with these lean bank codes for 2-3 years (wouldn't appear in the spring/summer months). Finally replaced my intake gasket. So far no more codes. Not awful... but time consuming to say the least. If you decide to pull the valve covers (waaaay easier to do with the intake out of the way), make sure you get the valve cover gaskets WITH the valve cover bolt grommets. I had to do the job twice as I used the original grommets (oil leaking around the bolt heads). Good luck.
 
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