Help me pin point this rought idle...!

[12Ounce]

Thanks, Ed ... I edited my goof!

[Ed_Strong]

Update:
I'm also a goof! I re-traced the plug wires and saw I had crossed plugs 4 with 5... what a dork, LOL (with all the precautionary measures I took)
Anyway, switched them back and it started ok and runs better, no backfiring, didn't smell raw gas. but there's still a hit of burnt plastic or rubber and the old idle issue is still present but not as bad as when the original post, maybe the PCM need to learn?

Also the alternator is still disconnected and the vans started good, no weak start at all!

[12Ounce]

Glad you found that problem.

Have you tried gobbing up all the vacuum hose-ends and vacuum tube ends with petroleum jelly for a really good seal?

[Ed_Strong]

Will a DPFE sensor go bad without throwing a code? All the posts I've read have had a CEL code set announcing it's demise. To this day I have not got a CEL code of any kind, (the CEL lights up at KOEO by the way). I should be getting an EGR code, right?

The Ford CD lists the DPFE as the first item to check for a rough idle condition. From what I understand the reading value should be between 45-55volts, is that a fact?. The manual says to check with scan tool for DPFEGR (hot idle value within 0.15v of KOEO value)

At KOEO I get a value of 1.21volts, and at idle it jumps to 1.24volts. If my numbers are right, that should indicate a faulty DPFE sensor. What do you think?

[12Ounce]

A DPFE will only give you a rough idle by opening the EGR valve at idle ... which should never happen.

So if you determine that the EGR valve fully closes off flow (most of them do) and is not stuck partially open .... and if you then remove and plug the EGR valve vacuum control line ... you have taken the EGR system totally out of the picture. (I think.)

Does the engine still idle rough??? ... if so, it ain't because of the EGR. There's gotta be something else ... such as a intake vacuum leak ...or an unhappy idle air control valve ... or, etc, etc.

[Ed_Strong]

Do you know what the scanner value should be for the IAC Valve? I cleaned it really good and TPS and TB as per first post, so I automatically ruled it off.

I applied man vacuum to the EGR valve and now the engine stalls as it should! Both lines for the DPFE hold vacuum when applied, but the voltage still roams between 1.19 - 1.24v, not sure if that where it should be...

[Ed_Strong]

I took the van for a ride with the scan tool connected and it took a good reading of the (%) value for the IAC, it changed accordingly to foot pedal poosition. Not sure what oder tests to perform on it.
But for some reason it won't read voltage values of the IAC to see if theres any fluctuations.
The DPFE on the other hand was jumping all over from 1.19v - 3.04v at different driving scenarios. Is that normal behavior for the DPFE?

[busboy4]

Hi
I don't know the exact values you should be seeing on the DPFE, but it would seem it should fluctuate based on differential pressure across the unit. I sense you know this but just to be certain: the DPFE is only a "passive" device measuring the EGR open/closed condition by differential pressure. The device that "controls" the EGR as commanded by the PCM is the EGR control solenoid on the back of the plenum :
http://info.rockauto.com/Airtex/Detail.html?2F1128.jpg

I would think that if the solenoid is commanding an open position when it should not that the DPFE should sense this and you would pop a code (P0402 perhaps). Anyway, keep looking for a vacuum leak - try vacuum testing the solenoid and the vacuum line(s) to and from it.

Good Luck

[tripletdaddy]

I believe in 03 I had a pair of problems. First the cat element rattled around till it turned sideways and plugged itself. Unfortunately on the same side as the egr tube. So, I had straight full blast exhaust backflowing up into the engine compartment through the two ports of the dpfe. It was a nightmare as I was taking my family on a summer trip to the lake on a hot day and I couldn't get it fixed well under the hood so it wouldn't melt any more than it did. I'm not sure if that caused my dpfe to go bad or just accelrated it going back. It did code a couple of times I think after I fixed the cat, I can't recall if it did on the trip or not, though I thought it should as is was measuring no pressure difference as the hoses were burned off. Anyway, cleaning the dpfe inlets didn't get it to work. It was an aluminum casting that was breaking down. Interestingly enough, I tested it according to my manual and decided it wasn't right so I replaced it but tested the new one too. The new one had identical results!?! D*mn manual!?! New dpfe is black polycarbonate, so hopefully won't crumble from the heat. Took apart the old one. Only problem with it was it was plugged up deep inside it that drilling is out wouldn't have worked, but electronically it still was functional.

Ok, enough chatter.

To make these measurements, the dpfe has a three pin wire connector. For orientation looking at the inside of the connector, the holding clip is on the right and a groove for mating with a ridge on the dpfe is on the left. The signal pin is next to the groove at the top, the middle pin is ground, and the bottom pin is the reference.

The book says with key on engine off, backprobe the wiring harness while connected (it says the dpfe should have the reference voltage for it printed on it):

VREF 4.0 to 6.0 volts

However, mine was backwards, I got on both dpfe units:
VSIG 5.0 to 6.0 volts (maybe ford has mine backwards?)

The book had no value for this, but I measured this
VREF 0.66 volts
Vgrd 0.05 volts
Looking at this with fresh eyes, I wonder if Haynes labeled their diagram wrong

With engine on, book says:
Cold (no egr)Vsig 0.20 to 0.70 volts
Warm (egr on)Vsig 4.0 to 6.0

EGR vacuum regulator
30 to 70 ohms

Turn key on, pull egr vac reg connector
should get battery voltage at connector
It appears the battery pin is next to the bump on side of the connector.

[tripletdaddy]

Well, I went to my van to check things out this morning at about 20 degF. I think that would constitute a cold engine. I tested for the spec voltage and also verified wiring etc, to settle the proper pin connections.

First off, Haynes is wrong, it's backwards, so I will give it by wire color to straighten things out. I did also checked Haynes wiring diag and that agreed with what Ford has.

KOnEOff
BAT 12.15v

FWIW with the harness off the dpfe:
Vsig 5.08 - Brown/Lt Green
Vgrd 0.11 - Gray/Red
Vref 5.08 - Brown/White, by bump on side

Harness connected, backprobed measurements:
Vsig 0.59 BR/GN on mine was top
Vgrd 0.11 GR/RD middle
Vref 5.07 BR/WT by bump on side, bottom

Eng on
Vsig 0.75 @cold idle - 1.0 @ high rpm
Vgrd 0.3
Vref 5.25
Note: Coiuld not get hot eng meas as van was leaving.;(

Maybe try running engine, go for drive without dpfe connected and see what happens. I think, with it disconnected it will get worse if it is ok and no change if it is bad, but you need to be sure the egr and egr solenoid are ok first. If the dpfe is ok and you disconnect it, I would expect a cel for that. Good luck. Let us know what happens. Thanks

[Ed_Strong]

I pulled, checked and tested every vacuum hose and they all check out good. Also I put the old spark plugs back on the engine to no avail. Still No CEL to track and scanner checks out all Injectors working "A" ok. Unplugged the IAC Valve with engine running and idle slows down to a stall.

I tried testing the DPFE Sensor with the harness OFF and Key On and got:
Vsig 4.99
Vref 4.99
didn't do the ground testing (forgot that one)

Couldn't do the back probe with engine running since my meter probes are too big to fit the back of the harness.

Do you have the specs to test the EGR Vacuum Regulator? How does one applies that one?

[tripletdaddy]

When I can't get to a metal contact, I learned to insert a sharp sewing pin through the wire insulation or in your case, a pin or other slender metal piece like a stiff wire into the back of the wire connector alongside the wire. I don't think the ground measurement is particularly important, but I like to see if it is close to 0 volts. I certainly would think there is a problem if it is high.

Maybe you didn't catch it earlier, but I'll elaborate more now. To test the egr vacuum regulator, pull the wiring harness off. Then measure its resistance across its two terminals. Normal range is 30 to 70 ohms. Outside that I would assume it is no good. Now you should also check to be sure it is getting proper voltage. So, with key on, engine off, check for full battery voltage inside connector.
It appears the battery pin is next to the bump on side of the connector. The other contact is the signal receiving wire to the computer, so it shouldn't be much if any.

[Ed_Strong]

<<Saga continues>>
Friend of mine (a Ford Tech) stopped by today:

Plugged his scanner to the van, no codes and no issues with engine systems. He couldn't find anything to indicate an electronic component malfunction. He feels that the rought idle is that the engine is off balance.

He took of the accessory belt off and ran the engine without it while inspecting the damper for out of balance rotation and nothing, same rough idle problem. He then sprayed the intake and plenum with some fluid and nothing, same idle problem. He went underneath with a big craw bar and wedged it on the back of the engine to lift the engine while in idle, I guess to rule out the possibility of a engine mount gone bad to no avail.

He left with the VIN No. to check the OASIS system to see if there's any other similar incidents and what's the outcome. He feels strongly about the off balance issue. Next step would be to disconnect the Torque Converter from the engine to see if idle returns to normal, but he wants to be sure before we start taking things apart.

This is getting ugly, we'll have to wait and see!

[12Ounce]

Wow! You've got a real mystery going on. There's not many things that would give a low rpm out-of-balance that wouldn't be even worse at a higher speed.

Bad tensioner resulting in loose cam chain? Something loose on the crank?

??

Good luck.

The engine isn't that bad to rebuild ... then you know for sure. But there are a 1000 other things to do first ....

[12Ounce]

I've reread this whole thread ... your problem seems to have started when you changed spark cables. I have two suggestions:

1. Again replace your plugs. I'm going to update my tranny/engine thread with what I happened, by chance, to "learn". Read the latest there.

2. Disassemble and inspect the whole upper (and spacer) area of the air intake. Maybe some plastic plenum got cracked, or something, when you were reaching the rear plugs ????