Hey guys, I just had the exhaust manifolds, studs and egr tube replaced last week. I've had these two lean codes since May, so I figured it was due to the exhaust leak. After the manifolds were replaced, I cleared the codes out. The truck is running well. After about 80 miles, the light came back on. There is no rough idle, stalling or surging at it. It maintains idle around 650rpms. My mechanic checked out the fuel parameters today with his scan too and told me that the downstream 02 sensors are reporting a wrong a/f ratio. After reading this bulletin, it sounds like that isn't possible. Could it be the vaccum hose even if it's running smoothly? I'm gonna catch more **** from the old lady if we have to spend more money on this truck and the problem still exists. BTW, the truck is a 98' 5.4 with 157k on it? Any input is appreciated.
Tommy

 

Here's some pictures for everyone. http://www.azda.com/ford/

 

Yes it is very possible to have this issue with it running smoothly, I just went though it. I had the CE light on and got the same codes, running lean on both banks but the truck ran great. I looked at the elbow right at the PCV valve and sure enough, that one was cracked. Changed the elbow with some CC breather hose from the parts store $3.xx and it fixed it. Cleared the codes over a week ago with no issues since. Got the hose instead of the elbow because it was cheaper and I have extra on hand if the rear one ever fails.

 

I have a 98 also and I had the ce light on for awhile with no symptoms, then the idle got worse and worse, I replaced all the elbows shown in madsonp's post and voila! everything has been beautiful since!

 

Thank You all!! Just found this forum and man!!! My Expedition just died at a light the other day and when I restarted it I got a CEL and it wouldn't idle!! Its a 2003 4.6 4x4 XLT.

So, off we go to the dealer to get the codes read and by the time he's done the qoute is $830.00...after the paramedics revived me I went home and found you guys.

Went out and opened the hood and yep, there was a nice hole in the boot! 5 mins. later and she's all siliconed up and runnung like new!!

Went and grabbed the Help! part mentioned and now she's good for another 100K!

So Thanks again for saving me $820 bucks. Who do I send your guy's cut to?

 

Glad we were a help to you, and welcome to the FTE forum.

 

Not sure what type of silicone you used, but one thing you, and others contemplating this type of repair need to make sure of is that the silicone you use is O2 sensor safe, otherwise it can kill your O2 sensors.

 

Excellent point madsonp, I should have mentioned that.

I used a O2 safe silicone and it was only on for an hour or so before the boot was replaced.

 

So....7 1/2 years this thread has been running and still worthy of a bump.

I've been chasing a P0171/P0174 CEL for a week now. Knew it was a vacuum leak, but dang if I could find it. This thread directed me straight to it. Well done!

 

My 1999 Navigator has the exact same problems. I have put a new Volant cold air intake on it, installed 4 new 02 sensors, installed a new fuel filter, looked at and closely inspected all boots and hoses and still can not locate the problem for the "missing." Do you have any suggestions on what I should do on my 32v? I do not have the rubber boot on the back of my intake like the regular 5.4's have. I have the large dual throttle body that is oval shaped. A non-32V is the single throttle body and is round. I can not find discussions for my motor anywhere but it seems to be having the exact same problems as your expedition. HELP PLEASE!!!

 

Tapenick- thanks for the hints. Maybe you can point me in the right direction? I have a '99 Navigator with the 32v Intech motor. I have the double intake throttle body that is oval shaped which is different than your single intake, circular throttle body... I can not locate the boot on the back of my intake and I'm thinking that my intake simply doesn't have it because it is different than the regular 5.4's that are not the 32v? Or- maybe it is located somewhere else? I have followed all lines from the EGR Valve on the passenger side and the PCV Valve on the driver side and there seems to be only one boot that attaches to the intake but it is on the passenger side and is very easy to access. Any ideas? I have replaced all 4 o2 sensors, installed a new fuel filter, installed a volant cold air intake and now it idles fine but when I step on the gas it runs like it is on 5 cylinders and misses like crazy. I ordered a new MAF Sensor hoping this would solve the problem because I can not locate any vacuum leaks anywhere...

 

Do you have the 32v Intech motor by chance? I do and can not locate this part that everyone is referring to which makes me believe that the 32V does not have this at all or is located in a different place?

 

Is your Navi a 32V Intech motor by chance? Mine is and I can not locate the elbow at the back of the throttle body. I'm thinking that my throttle body is different because it is the dual intake and is oval shaped.

 

I have the same problems. Low idle, check engine light. But my dilema is I don't have that vacuun assembly everyone else is talking about!! I was so glad when I found this thread thinking, Oh yeah, this is going to be a snap. Do Canadian Expeditions not have this part or something? I have the 5.4L Triton, but no assembly.

Any ideas? I am taking it in to the garage this afternoon, but I'd like to be able to fix it myself.

 

Please post what you find out!