5.4L Rough Idle - EGR block off didn't fix
 

So a few months ago my Expedition (5.4L) threw the code for the DPFE, the truck started running rough, hesitations, no power, horrible gas mileage, etc.

Before I could replace the DPFE (funds), I tossed a piece of aluminum can between the EGR and the manifold to see if that would make the symptoms go away, it didn't. The rough idle/running is still there, so I parked it and used it only for emergency trips.

I then replace the DPFE and the code is cleared but the rough idle/running still exists, I'm curious if anyone has any ideas what it could be now since I had the EGR blocked off and still had the rough running. Anyone have any ideas? I've got to get this thing back in operation for a camping trip in the middle of August.

Thinking I need to clean the IAC and then spray around the engine bay with some carb cleaner to see if I have a vacuum leak. But wanted to start a post here first.

Thanks for any help

Adding link(s) to DPFE troubleshooting thread(s):
Focus Shacks - DPFE Sensor and EGR Information

Good idea to do this first. Don't be shy with the cleaner, give it a good soak and spray.

Will do, tearing it apart tonight once the heat gives me a break. Oregonians don't do well once the temp goes over 70. :D

I suggest that you do a "google" search for "DPFE". There is a post listed from the Focus forum that has a great description with pics in regards to this sensor and it's operation.
It's not always the item that the code reader seems to pinpoint that is the real problem, It is often something else in the system that causes the item pinpointed to malfunction, which in turn causes us to start by replacing the item the code reader specifies and then we eventually find the base cause of the problem. We have to remember that code readers are only tools to aid in the diagnosis and repair of a problem.

This is gonna soumd dumb, but does the computer have to be reset after this procedure? Maybe disconnect the battery for a day then see what happens when you fire it up. Good Luck!

It would be helpful to me to know the model year of this 5.4, the specific DPFE DTC code, if there were any other codes, and the number of miles on this vehicle.

This can cause a P0400 or P0401 DPFE code.

More than likely the infamous PCV elbow at the back of the intake manifold is leaking, and is not related to the EGR issue.

Thanks, I'll look for that thread and then link it here at the top so others who run across this can quickly find it. :-X22

Yes, you should disconnect power to reset the ECU however you only need to pull it for 10 seconds to make sure all power is out of the system. I typically will pull it after tearing everything apart and then put things back together so I can just reconnect the battery as the last step of assembly and there's no doubt I didn't leave it off long enough.

It's a 2003 with 120k and I believe it was the 401 code. I foolishly didn't pay attention to what specific code the NAPA guy pulled and he just told me it was the DPFE sensor. The other flag for me was that when I looked at my DPFE one of the hoses was completely destroyed on the inside (with a small hole leading to the outside) and it had melted half of the stem off the original sensor.

On my 2000 expy also with a 5.4 I had could for high DPFE Flow(I don't remember the number) it was one of the hoses going to the sensor it had hole burned in it both hoses were very brittle so I replaced both of them. if that is the problem need to get the hoses from ford dealer not they are not just vacuum hoses.

When I was doing an engine change in my Navigator I found that the OEM hoses were disintigrating from the outside as the rubber was flakeing off on my hands by just touching them. The hoses seemed to still be good and firm otherwise but, I replaced them with high pressure fuel hose and 3 years later they are still doing fine. I check them whenever I'm under the hood just to be sure. Better safe than sorry!

Okay so I let the truck sit for a long time due to an overwhelming schedule and what not. Finally got around to it today and first off the battery was dead from me letting it sit forever. I jumped it and was surprised to see that the idle was normal. I let it warm up and the idle stayed fine. Then I decided to take it for a trip around the block. Everything is fine at light pedal pressure or at idle but once I need to accelerate, she falls flat on her face.

I'm about to rip her apart right now to clean the IACV but just wanted to get an update out now.

Cleaned out the IAC...did some more experiments. The issue is only when given a large amount of throttle at once. If slowly added there are no issues, if added in one big chunk, like trying to accelerate quickly to join traffic, she gets all lumpy and nasty, then settles back to a smooth idle.

Are you getting any codes now?

Hey Mel,

No codes since I replaced the DPFE. Just cleaned the MAF and waiting for it to dry before testing.

Well that pissed her off..rough idle has returned, almost like she's missing....trying to unplug the COPs one at a time to see if there's a point where nothing changes....damn it's hot in there. :)

Still no codes.

Unplugged the #6 COP and conditions did not change. Game on.