I'm trying to fix a stumble/hesitation issue at 12-1500rpm with my 98 expedition 5.4.

I tested my dpfe and the top wire was around 1.40v or so with NO vacuum applied to the hose. One I added suction, it stopped at 4.94v.

So according to the ''test dpfe'' thread my sensor is bad, but would it cause my stumble? I've also read that a weak diapham spring in the egr could cause this. I have no codes stored in the pcm.

After running the truck with the DPFE unplugged for a couple days, the truck ran great, no stumbles and seemed to have more power in general.

So today I grabbed a dpfe from the j yard hoping to get lucky. Installed it and still had the same problem.
Tested it and this sensor was reading 1.0v with no vacuum.

Thoughts?

 

After replacing the sensor did you disconnect the battery for a few minutes to clear the memory?

 

Yes,still the same issue.

 

any thoughts?

 

I would start tearing into the EGR system. When you had the DPFE sensor disconnected the EGR was disabled and the truck ran good. Remove the valve and check the passages behind it to make sure they're clear.

 

Will do. If the passages are clear then most likely the egr valve is bad correct?

 

Without doing any tests to confirm, all I can say is that it's a possibility. Take it a step at a time, first check the passages and go from there.

 

Here's a PDF of the EGR Pinpoint Tests, if you're so inclined.

 

I would pull the green vacuum line off the egr valve and check and see if you your stumble

 

Pulled the vac line and plugged it, stumble was gone.

 

I believe you have 1 of 2 things going on, or both, the egr has a weak spring and the it is allowing too much inert gas in and stumbling until the pcm can correct it, or the evr cant limit the vacuum the way it should during cycle tests, and in crusing, or both are bad, my thoughts

 

I would think this thought of yours is more likely than the weak spring one.

 

Is the DPFE considered the "evr? If not, where is that located?

 

I had a terrible stumbling problem with my 97 Expy with the 4.6L. I did everything you mentioned and more. It turned out the upstream passenger side 0@ sensor went bad due to a manufacturing flaw. The condensation drain for the A/C empties onto it. After i replace the )2 Sensor and did the recommended solution which was a piece of hard plastic vacuum line to divert the condensation away from the sensor all of good and the stubble went away. There were day when it got so bad I thought it might die at the light. Hope that helps, since I did the whole EGR thing, pulled the throttle body and cleaned the ports, I even replaced the vapor canister and solenoid ont he gas tank. I literally went from front to back and 2 years later found out that Ford had this issue and they had a service bulletin out on it.

 

the evr is at the other end of the green line, round cap with white vacuum line that is constant engine vacuum, with a plug