The DPFE is a "Differential Pressure Feedback EGR System Monitor" It's located at the rear of the engine. There are 2 hoses to it and with the sound you're hearing it probably has the hose off or the pipe is rusted. Check the hoses and see if one is off. Here's what the DPFE looks like so you know what you're looking for:

 

I found that off the NAPA web site but I wasn't sure that was the actual picture. After seeing the picture, I still didn't see it though maybe I was just missing it. Can you be a bit more specific about the "rear of the engine?" There is a lot of space under there and that still leaves a lot of room for error, if you know what I mean. I believe it's connected into the same line as the EGR (I do know where this is) looking at the diagram in the repair manual. Is this true?

 

Tht's where it connects, to the EGR tube. Take the cover off the engine and you can see it just to the right rear upper. It's in a tough place to get to but you can see it. Reach down and see if the hoses are intact. they might have deteriorated nad you need new ones.

 

If this photo is correct for a 99, that's what is being unplugged here.

 

Alright, I will check for it in the morning. I have had the cover off a few times but have always been looking to the left side of the engine as this it where I believed it was (for whatever reason). If I'm understanding you correctly, it shouldn't be far from the brake system (master cylinder) which is also on the drivers side. I would bet that I do need new hoses though as the car is getting quite old, has a lot of miles, and is always parked outside. I will check it tomorrow and post back if I have any more problems or questions. Thanks for your help!!!

 

Those hoses are special because of the exhaust that puts pressure in them.

 

What do you mean they are special? I know I have to get the proper ones at the auto dealer. But before that I have to find where the bloody thing is.... :/

 

@jwko I'm not sure that's what mine looks like though not being in front of it I'm not sure. The EGR is on the passenger side of the engine and looking at this picture it's showing it on the drivers side (I think). Honestly if I had a good and definite picture of the thing I don't think I would have any problem finding it, I'm no stranger to an engine, though I truly do hate the emissions control system.

 

I wasn't for sure. I got it from autozone's repair section & sometimes (I guess) their photos are meant to be universal.

 

I got the exact same picture from NAPA but I don't see anything that seems even close to that under the hood. I pulled off the plastic cover that's over the engine even and there is nothing under there. I suspect that is a generic picture and the one on my car looks different, though I'm not sure about that. The EGR valve picture from NAPA is dead on, however.

 

Oh, and I suppose that I should mention (whether it's relevant or not) that I can smell exhaust fumes when I stop and idle or when I am driving very slowly (<5MPH give or take). This also leads me to believe that one or both of the hoses have failed.

 

I still can't find the little bugger. I went out and looked twice but maybe I'm just missing it. I see the EGR right where I would expect it but I don't see any sign of the DPFE connected to the exhaust lines. I shot a few high res pictures with the hope that I am just missing it and that maybe somebody could point it out. The pictures are here: Index of /Photos/Engine Please be warned, they are fairly large images and may take a moment to download.

 

I finally found it, this was the aha! moment when I saw this picture: http://www.p71interceptor.com/airintakeplenum/pictures/PICT4659.jpg and realized it was way down behind the engine. Sure enough, the hose was just hanging off. It's been reconnected and I cleared the code so we will see what happens (I don't expect it to come back). Thanks everyone for your help!

 

Thanks for letting us know. I was about to tell you it was below the heater hose connection at the right side and you beat me to it. If it blows off again, you might have a plugged catalyst. Hope it was a fluke, old hose getting worn.

Have a safe trip.

 

rtg143, you again saved the day!!!
good job.
I found that little burger by accident also. As you looking at the engine from the front of the car you go to the left head and way down at the back and toward the bottom of the engine: well there it is. Its a tight and hidden fit.
have a good day

 

Something didn't seem right when I reconnected it but stupid old me proceeded anyway. Not to long after I fired it back up, the light came back on, same code. I pulled the sensor off and it was melted, rather badly. So again, stupid old me bought another one and put it on, it melted as well. I pulled it off, along with the hoses and the hoses look alright other than the one being damaged at the end where the sensor was melted. My initial though on this was a plugged cat converted but I would think that I should experience other issues along with this (more codes, loss of power, stalling, etc.) and I don't see any of those. I have attached a pic to show the damage along with the two hoses. From what I understand, this is the engine side of the EGR hose, the side that's alright is the EGR side I believe. Anyone have any thoughts on this? Seen this happen before maybe? I don't want to replace the hoses and the sensor again if there is a bigger problem here. Any help would be appreciated.

 

The exhaust doesn't go through the DPFE. if the hose was loose, the exhaust would be coming out of the hose and that would be pretty hot. Normaly the hose just has exhaust pressure to sense and nothing comes out. Similar to an oil pressure sensor. The hose may have been loose and let the exhaust between the hose and fitting.

If you want to check for a plugged exhaust, get a vacuum gauge and see what the engine vacuum is when you run the rpm up. It should be aprox. 20" at idle and when you run the RPMs up it should drop to approx. 5" or so and go back up to approx. 18". If it drops and barely comes up you have a problem. (These readings aren't carved in stone just for reference.)

 

That's what I was starting to conclude here this morning, that there is no flow through the sensor. It's just looking for a pressure difference between the two sides, correct?

At the most, if the cats are plugged, it could in theory simply blow the hose off. I know a few people that are mechanics and they might have a vacuum gauge. Where do you check the engine vacuum?

 

You could tee off the brake booster or even just use that, since you won't be driving it during the test. Did the hoses go on real east? you might be able to cut a 1/2" of the end and it would be tighter if the cat isn't plugged. Or get new ones.

 

Yeah, they did go on fairly easy, and the one from the exhaust side has a bit of a crack right where it connected into the DPFE sensor. I will probably just get new hoses, these are 10 years old, I'm sure they have never been replaced.

 

I found the hoses today at the local NAPA, and after trying to fit them into another new DPFE sensor, they old hoses went on REALLY easy. I had to fight with the new ones to get them to squeeze on to the sensor. I'm leaning towards the hoses at this point but am headed to have the vacuum pressures checked out tomorrow at a friends house. I will let you know what I come up with, if the cats check out alright, then I will just put it all back together with the new hose and sensor and call it good.

 

Sounds like a good plan. Will be waiting to hear.

 

Alright, so I got hold of a vacuum gauge from the auto parts store where my brother works and just completed the test. At idle, it sat right about 21". When I reved it a bit however, it didn't drop all that much, maybe down to 16" or so. When I let off and let it return to idle, it went back to about 20". From your post, I would have expected it to have dropped a bit lower at higher RPM but it didn't seem to. I ran it pretty high though since there isn't a tach on the dash, I couldn't be sure what RPM I hit. Thoughts?

 

With those readings, I'd say you don't have a plugged exhaust system. If you hit the throttle hard, it would drop more and go back up. I think you're set now with the new hoses.

 

That was my feeling as well. I don't think I'm going to do it tonight (though I still may) but I will most likely do it tomorrow before I leave work as I know the car will be good and cool so I don't burn myself on the EGR line. I really appreciate all your help with this, thank you so very much, I owe you one!

 

No problem. We're here to help.