In my never-ending search to fix the mild ping in my 99 5.4, I found some info on testing the DPFE sensor. I hooked up a voltmeter to the top wire in the harness and applied vacuum to the front-most vacuum line and got no reading, I read somewhere that it should go from 0-5 volts when vacuum is applied? I was, however, able to cause the motor to run rough by applying vacuum to the EGR valve at idle. I have always supected the EGR system for problems because of my pinging and high-pitched whine when I let off the throttle. Is there any better way to test the DPFE or am I just 'looking for pings in all the wrong places' ? i have already cleaned the EGR, IAC and TB but none were very dirty. I ran some seafoam throught the brake booster and got virtually no smoke. Something has got to give! As always, any input is appreciated.

Btw here is the info I used, cut and pasted from another thread on these forums:

There has been a lot of talk about the DPFE sensor going bad so I thought I would post a "how to" test the sensor. You will need a volt meter, safety pin and a 3 or 4 ft piece of hose (about 1/4" ID). If you know where the sensor is located skip to the next paragraph. Remove the black plastic cover (3 screws) exposing the throttle body and other fuel related things. Its the cover in the center of your engine that says something like 5.4L or 4.6L on it. Now the DPFE sensor has 2 rubber hoses (about 3/8" dia) coming off the bottom leading in to 2 metal tubes which are leading into a 1" metal EGR pipe coming off the exhaust manifold. On the side of the sensor is a 3-wire connector. This assembly is the DPFE sensor.
Remove the 2 rubber hoses from the bottom of the sensor. Attach a piece of rubber hose to the forward most hole in the sensor. Now carefully take a small safety pin and stick it in behind the top wire parallel to the wire. You do NOT want to pierce the wire, only make contact inside the connector. This top wire is the active feedback signal wire. It will vary from 0-5 volts or so. The middle wire is ground. The bottom wire is 5-6 volts supply. Now the top wire voltage will vary as the pressure between the two holes in the sensor varies. Set your meter to read volts, either turn the key until the accessories are on or start the engine, either way is fine. Now using your mouth apply suction to the hose and you will see the voltage change from near 0 to near 5 if you apply enough suction. The vacuum on the hose should hold your tongue and not leak. If the voltage does not vary or is stuck high or low, the sensor is bad. Do the same thing to the rear port but the voltage difference will be much less, this is the reference port.
If the sensor seems to be working then you can further test the system by doing the following. Attach the hoses to the sensor as normal. Now remove the rubber vacuum hose from the top of the EGR valve diaphragm. With the truck running apply slight vacuum to the EGR valve and this will open the EGR valve. When the valve opens you will see the voltage on the top wire of the DPFE sensor change indicating flow. When the vacuum is applied your truck should stumble or almost stall indicating the EGR valve has opened which it normally does not do at idle. You can buy one online from http://www.fordpartsonline.com/ for $65. I hope this helps.

 

Hmm.. You tested the DPFE sensor according to the posted test (which is accurate) and it failed..

Tell me again, what's your question???

FWIW, a faulty DPFE sensor should have turned on the MIL with a P0401 or similar code.

Steve

 

As Steve said, you should have gotten a code if the DPFE sensor was bad. My '01 4.6 set a P0402 when the DPFE went bad. Is your CEL on? If so, go to Autozone and have the codes read. Repost when you find out what the codes are.

Anthony

 

No, the CEL isn't on, and the truck runs fine and has plenty of power. It just has this spark knock condition that I can't put up with. Otherwise this has been the truck of my dreams, but I recently listed in in the autotrader. I hated to do it, but I felt like I had to. If I could fix it, I'd do so in a heartbeat. I have had a very good mechanic who is a friend of mine look it over and listen, and he says that it is very minor and not to worry about it, and that it probably can't be fixed without pulling some timing. The truck is perfect in every mechanical aspect, I was just hoping to find a simple fix with the DPFE. Tis a depressing situation...

 

If the DPFE is not working it will cause it to ping. It may be "within spec" and not turn on the CEL but still not be fully working. I have seen that happen with many other sensor I don't know why this one should be any different. When mine went bad, my 4.6 sounded like a thrashing machine it was banging so loud.

Good luck.

 

How would a bad DPFE cause it to ping? Basically, what does the DPFE do if it is working properly, and what happens when it craps out?

 

I still disagree with WVtrucker. If the DPFE is faulty, you will get a CEL. You can find out exactly how the DPFE system (or any other system) works by going to this website, searching for your vehicle model year, then scrolling through the techinical documentation until you find the system (i.e. EGR, Missfire, etc) that you are interested in. Best of all, it's free!

Anthony

http://www.motorcraftservice.com/vdi...&menuIndex1=27

 

Actually a faulty DPFE may not cause a CEL under certain condtions, we had many come through the door with bad DPFE's and no light on, and a bad one will cause a pinging concern due to the fact it regulates EGR flow by sensing the flow through the EGR tube, if the PCM is seeing what it thinks is too much flow it'll cut back the signal to the EGR solenoid which in turn causes you to run a bit lean, hence the spark knock

 

So the EGR is operating too much or not enough with a bad DPFE? What would happen if you just temporarily unplugged the DPFE connector to experiment with results?
If I knew the DPFE was bad, I'd replace it. The thing is(with this pinging) it could be so many things! I have already knocked out a few possibilities, but at this point I'd have to replace parts to see if they were bad. I can't afford to just throw parts at this until it is fixed! Is there any better way than SWAG to track down the culprit?

 

With a bad DPFE the EGR won't be opening enough or not at all depending on what the signal it's sending to the PCM but before you go and buy one... when does this thing ping the most .. ie does it ping when the engine is cold or only when it's at normal operating temp? under accel? or cruise? and finally did you run any kind of cleaner through the engine to be sure it's not a carbon thing?

disregard that last ? I reread your first post

 

After I reread it again are you sure you don't hae something as simple as a \/acuum leak?

PS sorry about the \/ thing but my \/ key stopped working lol