ok, got a 98 expedition with 154500 miles with a 5.4l. problem that i am having is that i have codes set for lean on bank 1 & 2. When the truck is cold i have no problems, but when the engine warms up it runs like crap. when its warm and i am at an idle like at a stoplight, my rpm's will drop down to 300 and bounce up a few hundred rpm and it will sit there and bounce till i put it in neutral or go. it has died a few times when its sitting still. it gets really rough feeling and it feels like it is missing on a few cylinders almost. the fuel mileage also has gone downhill alot also. i have replaced the plugs and coils, mass air flow, o2 sensors (all of them) ugh hated those, egr valve. I am beginning to wonder if its not my idle air control valve that is making these problems for me? what ya think? thanks

 

Inspect the PCV system hoses for cracks, especially...and I do mean especially...the elbow at the rear of the intake that feeds the PCV system.

 

Expygirl,

I just resolved the exact same issue on my 98' with 275k mile and now it has never run or idled better. I learned about the potential causes of this condition (i.e. dirty throttle body, dirty IAC, vacuum leak, dirty MAF sensor) Initially I was just going to replace the IAC, but getting to it was hard due to its location. I was encouraged to see that it was not that hard to take off the entire TB and adapter and work on the entire assembly on the bench.

In short, thats what I did. I was best able to view and swap out the bad hidden vacuum fittings, clean the throttle body and adapter, change the IAC and MAF.

Follow my thread and click on the links that others provided. THere are great pics to ease your mind.

https://www.ford-trucks.com/forums/1...ion-5-4-l.html

 

Alloro, as uasual, is spot on. I never saw this elbow until I removed the TB and adapter and even then, I needed to get a good angle from a step stool.

Because I did so much (cleaned TB, MAF and ADAPter, changed the IAC and swapped out all the vacuum elbows it's hard to say what it actually cured my issue, but I venture the latent leak in the vacuum elbow on the intake was the cause.

To test, I sprayed some throttle body cleaner at the vacuum lines and elbows to look for a change in the idle. In fact I got a leveling when I sprayed it on the lower EGR connection on the adapter. What I didn't know until later was what was really happening was the cleaner was entering that lower elbow on the intake causeing the leveling. BE CAREFUL doing this, obviously. THe stuff is flammable.

Know that I am a shade tree guy and knew nothing about what I undertook. THis forum has all the answers. It took me about 4 hours and best of all my out of pocket was about $75-$80. I'm sure the savings was in the thousands.

BTW, I did it in an unheated garage on a snowy day and didn't get that cold.

 

thanks guy's this gives me some things i gotta do this weekend!! I hate working on my own stuff had a shop for 14 years and am sick of gettin dirty! but got to get this truck running better, i love my expedition and don't want it to die on me!!

 

Here is a picture of the PCV hose system with the throttle body removed. The PCV elbow in question is the one circled in red.

 

newbie here I just bought my pcv pipe and installe it on my 1998 ford expedition with 175k miles. then there's this y splitter is it fine I cover the other hose. because the pcv tube I bought doesn't have it or I need to cut the pcv tube and use the y splitter on it?

thanks for your replies

 

newbie here I just bought my pcv pipe and installed it on my 1998 ford expedition with 175k miles. then there's this y splitter is it fine I cover the other hose. because the pcv tube I bought doesn't have it or I need to cut the pcv tube and use the y splitter on it?

thanks for your replies