P0401 EGR Flow Insufficient, 5.0 L (FIXT)

[fixt]

1996 AWD 5.0 L
Check Engine light came on yesterday and scanned with Innova 3160 scan tool
P0401 - Exhaust Gas Recirc Flow Insufficient Detected
There were two P0401 codes.
The engine runs fine and I can detect no sputtering or flat spots. Idles fine.
I had reset the code and it came back in later at 32mph and 174F ECT according to data. Trying to determine when it came in, I called the wifey and it had not come back in today. Her work is about 5 miles away.

Since it seems to be intermittent at this point, would you think the valve is getting sticky and need cleaning or would you think the valve position sensor (DPFE?) is going bad?

I read about decarbonizing and cleaning the EGR which I am sure has never been done, as well as checking vacuum lines and testing the valve by applying vaccum.

There is a vacuum line to the EGR from the EGR vacuum solenoid. Is that the place to apply vacuum?

Is the DPFE at the electrical connector on the back of the valve actually a position sensor for the EGR? Its not the flat black pancake kind.

How do I need to pursue fixing this thing?
I don't know much about the emission system, I prefer simple old jeeps.

 

[jremington59]

You don't have a DPFE. That year had an internal egr.

 

[fixt]

Ha.
Well, I admit that is some help.
Anyway to point me toward fixing it?

 

[jremington59]

Ha.
Well, I admit that is some help.
Anyway to point me toward fixing it?

http://www.explorerforum.com/forums/showthread.php?t=259697

check the gasket on the sensor that operates the egr valve.

 

[fixt]

OK, thanks for the link
I will update when progress is made.
Being a tool *****, I got a stubby ratchet set along with stubby metric and SAE combination wrenches. Looks like those may be needed along with some band aids.

The mechanism on the back is the valve position sensor then?

I have no reason to suspect the gasket has been removed as in your case since has been operating fine (due to lack of codes). I will check as it may have gone bad.

 

[jremington59]

When you take it off make sure the egr isn't stuck closed with carbon. Lube up the shaft it slides on. It happens occasionally. But my guess is the sensor has gone bad.

 

[1998Exp]

The EGR valve position sensor in your picture is a simple potentiometer (variable resistor), so you can check it with a multimeter. Observe the resistance between the center and one of the other contacts while slowly moving the pin up and down. The resistance should vary smoothly (if memory serves, from about 100 to about 5000 Ohms). You can do this with the sensor removed, or if you have a hand vacuum pump, by hooking it up to the valve and slowly increasing or releasing the vacuum. Hope this helps.

 

[fixt]

Update
I pulled the EGR today and cleaned it, not too bad but it seemed sticky when applying vacuum. After cleaning it out it was less sticky and smooth operating. The position sensor was checked with a Simpson 260 so I could check the sweep of the position sensor. Range was from about 600 - 3200 ohms or so, no dead points. The EGR nuts did seem lose on removal, not so loose now.

Without the stubby wrench set I don't see how it can be done with the engine in the vehicle. Its tight for the bottom bolt, very tight. It helps to take vacuum relay off, out of the way. Clean your electrical connectors while you're in there. The bottom nut is a royal pain in the (imagination) to get back on, and I have smaller hands. Big hands stay out. A ratcheting stubby wrench would have been very helpful, but a stubby ratchet with socket would not fit under the EGR valve lip on the bottom bolt.
As stated previously, 9/16 on top and 1/2 on the bottom.

No codes, all reset, valve now operating smoothly.
All is good so far.

Aside, I have never used the corn syrup gas being made. All real gas all the time, and all vacuum lines looked real good from what little I could see. Maybe that accounts for the fewer valve deposits as well.

 

[fixt]

Resolved

As a final followup to the intermittent P401 code problem, I carefully monitored engine and mileage parameters. I still received the code occasionally for no apparent reason under different conditions.
No mileage changes or other conditions were noted.

I replaced the EGR valve position sensor using the included o-ring (shown above) and EGR valve gasket.
Position sensor part F2ZZ-9G428-B, CX-1464 from Rock Auto. All total was about $78.

Testing the position sensor with an ohmmeter showed a dead spot.
Its been replaced now for about 6 weeks with no recurrence of the code, so I'm calling it good.

 

[fixt]

Well Maybe Not

The annoying P401 came back
Checked freeze frame data, could not see anything amiss. Just seems intermittent, no similarities in freeze frame data when it occurs. Different speeds, rpm, temps, etc.
Checked the vacuum line from vac relay to EGR and the EGR diaphragm with a vac tester, no problem. It holds vacuum fine.

There's no apparent engine problem as it runs good with no hestitation or stumbles, smooth at idle, all that good stuff. Live data looks good too.

I'm thinking the EGR may be sticking on open signal. Maybe not opening smoothly and possibly the vacuum relay. I'll pull the EGR, clean it whether it needs it or not and lube the pintle with some high temp grease like brake grease. Maybe that will rid me of this aggravation.
I've ordered a vacuum relay and a 10 pack of EGR gaskets.

I use real gas, no ethanol. Maybe that leads to more carbon and requires more frequent cleaning, I don't know. Its not driven hard, pretty mildly in fact. Ill update on carbonisation on this next evolution.
CELs are worrisome and are not supposed to be there.

 

[1998Exp]

Sorry, overlooked the P401 and answered the wrong question. Please ignore.

 

[jremington59]

There's one sensor on the back of the EGR itself and another one that has I believe a couple small hoses coming off it. One of them goes to the EGR valve. That part could also be bad. Also make sure the hoses aren't cracked.

 

[Bill MacLeod]

Not sure if this will be of any help, but had a similar problem several years ago with my 95 Mustang. Intermittent code but different # with ODB1.
Replaced sensors, vacuum hoses, clean valve, etc without any success. Finally put on a new EGR valve and problem solved.
So I checked the old valve again with my vacuum pump. What I noticed was that the valve would "pop" open. You could actually hear the popping noise ever so slightly at about 4 to 5 inches. According to my shop manual, there is a self test at cold start-up where a couple inches of vacuum is applied, as well as other emission self tests. I can only assume that the vacuum at self test would not open the valve to pass the self test and therefore the check engine light.
Again this was ODB1 system, but something to check out.

 

[1996BLKBauer]

I had this code come up once, I believe it was sticking or something, because the truck ran like crap right before the CEL came back on, I revved the crap out of it(Short bursts to 5k, then back down), and cleared the code, seemed to fix my problem, it never came back that was over a year ago.

 

[Ol' Mountaineer]

I didn't have a vacuum pump handy, so I used a clean coolant tester instead - you know, the kind with a rubber hose at one end and a "turkey baster" bulb at the other. Engine properly stumbled when vacuum was applied. My EGR valve seems ok... though I didn't really get convincing results with the 20-second pressure holding test.

Not looking forward to removing the valve or the DPFE on my 5.0 V8. Someone really oughta tell Ford engineers to put short lived parts where they can be easily removed!

 

[fixt]

Update

I should have mentioned earlier, the codes were both P0401 and P0402.
EGR flow insufficient and excessive, at the same time.

I pulled the EGR valve and tested, cleaned, and lubed the stem as best I could while exercising the valve with a hand vacuum pump. The valve opened easily at less than 5" hg, the scale minimum indication on my tester. It did seem to "pop" off the seat when opening.
Very little carbon, but I cleaned it anyway, blew it out, and cleaned it again.
Applied some high temp grease to the stem with a Q-tip and exercised the valve. It seemed to open more smoothly. New gasket and all that stuff.
Its such a minimum vacuum its hard to tell, but it didn't "pop" off the seat as hard. Again, hard to tell.

I replaced the Vacuum regulator solenoid($22) and the vacuum line to the EGR.
Both old and new vacuum solenoids tested 31 ohms, I kept the old one for a just in case. The hard plastic white source line to the solenoid appeared in good shape.

It now has a new EGR position sensor with O ring, vacuum regulator solenoid, EGR vacuum line, and EGR has been serviced. No codes at this time, test drive was fine. The intermittent problem has never affected mileage and the engine has always run smoothly; I track mileage tank to tank.
(I know when woman runs the AC in the summertime by looking)

The Motorcraft EGR position sensor was $75, a 10 pack of EGR gaskets and vacuum solenoid was $53 with shipping. So far thats whats in it for an intermittent problem light.

The only thing left at this point would be a new EGR valve, about a 138K on this one. I'll watch it and see what it does. The Motorcraft valve is $132 from Rock Auto if that's how I end up.

Unfortunately I'm getting good at removing the EGR without even dropping the bottom nut. A pox on the engineer who put it there!

 

[fixt]

Resolved (really this time)

OK, No more intermittent P0401 codes to this date.

Perhaps the EVR was sticky when signaled to open the EGR or maybe the EGR itself was sticky, resolved for a period by lubricating the stem with brake grease.

I don't know which fixed it, but no more codes have shown themselves.

To recap:
EGR position sensor was replaced - $75, and probably unnecessary
EVR solenoid valve was replaced - $53, which included 10 pack of EGR gaskets at $18
EGR valve stem lubricated while exercising the valve with high temp grease. The valve was cleaned though it was not dirty. It operated smoothly and opened with <5"hg. Its smoother coming off the seat now as it "popped" off the seat when testing.

I "think" it was a timing issue of the sensed valve position not being correct when signaled to open. Codes appeared randomly.

 

[jay1028]

I just had to have the entire EGR system replaced.
http://www.explorerforum.com/forums/showthread.php?t=400985

I had a small problem at idle every once and a while, like a small misfire. No problems while driving and no power loss. Then a problem surfaced while towing. They replaced the entire EGR system, but I had them return to me the old parts. The position sensor and solenoid check out fine.

To really check if the EGR is holding a vacuum, you really need a DMM on the position sensor for resistance. A 260 will not give you enough resolution. When the diaphragm leaks, it is sometimes a small change over time. Enough to set a code but not present a driveability problem.

 

[fixt]

Updating this. The P401 code returned and quite frequently. I pulled the EGR and cleaned even though there was little carbon on it. Tested with a vacuum tester and there was no diaphragm leaks. But, when I tested the EGR position sensor there was a flat spot in the ohm reading, so I replaced the relatively new unneeded position sensor with the old one, which tested good throughout the stroke. That was about a week ago, and the P401 has not returned.

To recap:
The P401 code was originally resolved on replacement of the EGR solenoid.
The position sensor was also replaced, which developed a flat spot in ohmmeter reading.
P401 code returned, EGR was cleaned and position sensor replaced with original, a tested good sensor. Code has not returned over a 1 week period.
I still say damn that bottom EGR nut!

 

[mic98xlt]

Just a quick FYI, this is type of EGR discussed above is for the '96 - '97 5.0 Explorers, plus the early '97 Mercury Mountaineers with the internal egr.

Turdle:
Do you have the internal, or external egr engine? look on the passenger side header-do you see an Egr tube coming straight up off it? If not, yours has an egr position sensor. It does essentially the same thing as the dpfe.
The sticking EGR valve could have definitely caused the code

There always seem to be a lot of confusion about this one and the later 5.0 engines with the external egr which has an completely different DPFE system. I hope this will help others like me who were confused.