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'96 Ford Taurus. ? Shouldn't EGR valve open ?

I?m at my in-laws for thanksgiving so I volunteered to help them fix their ?96 Ford Taurus but I?m a little puzzled and need some expert help.

Failing smog test: There seems to be a problem with the EGR system , the check engine light comes on and the car, of course, is not passing the Orwellian California smog test. I looked at the report from the failed smog test: P0401 = ?Insufficient EGR flow detected?. Actually the tailpipe emissions measured are within spec but the mere fact that there is a 401 code is considered a smog test failure.

In trying to diagnose the problem, and looking at the ?typical EGR system description? in the Hayes manual, I can identify 4 possible causes:

  1. The EGR valve is not working
  2. The EGR valve is working but the EGR exhaust tubes are clogged up (I?ve seen this in an old Mustang I once had)
  3. Everything is fine but the EGR backpressure sensor is not working and is lying to the computer telling it that there is no flow.
  4. The EGR valve is not getting a vacuum signal to open in which case either a) the vacuum solenoid is not working or b) the vacuum line to the EGR valve is clogged or broken or c) the computer is not giving the right electrical signal to the EGR solenoid to open.

I decided that I could easily look at 1,2 and 4 (cause 3 seemed a lot more difficult to explore because this car has the Duratec 3.0L 24 valve engine so the backpressure monitor is in some inaccessible location below the intake manifold).

So I first explored cause 2? I took out the EGR valve and the short exhaust path from the EGR valve to the intake manifold looked unobstructed. So next I started the engine. Sure enough, I heard the exhaust noise coming out of the EGR line, but in any case I stuck a flexible metal line into, it in case it was clogged. Not much crud came out so seems like the exhaust path is open. So now I looked at cause 1? as I had the EGR valve disconnected, I connected it to the vacuum line and looked at the plunger inside the valve expecting to see the vacuum lift the plunger at least some but nothing happened. I revved up the engine and still nothing happened. My brother in law had already bought a new EGR valve so with the engine running, I hooked up the new EGR valve to the vacuum and still the EGR plunger did not move. I disconnected the EGR vacuum hose and put my finger on it and I can feel some very faint vacuum pulsing but it seems to me quite weak, besides I can visually see that the EGR valve plunger is not lifting at all.

So based on the above evidence, am I looking at cause 4 or am I missing something?

Reply to
ThomasE
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Basically, the EGR will only open with the engine under load. It will not open while free reving the engine. The most common cause of a P-0401 is a failed DPFE sensor. I usually recommend NOT throwing parts at a problem, but in this case, a new DPFE will most likely solve the problem. It's around $35.

Reply to
Tom Adkins

I second TomA's advice, bad DPFE is usually the cause of P0401. Had this happen on our 2000 24v Duratec in the Taurus wagon. Actually the car ate two of them, they have a high failure rate. DPFE only took five minutes to replace, look down between the firewall and the intake, about midway, there's one electrical connector on the side and the two egr tubes going into the sensor from the bottom. Work it off the tubes gently and plug the new one back in.

Reply to
sleepdog

Ditto the DPFE, same on my 99 Taurus Duratec. I was going to perform in-depth troubleshooting...and my local parts guy (who was a part time ford dealer mech) recommended the DPFE. I suggest replacing the two hoses, too, if your parts store carries the right stuff (rated for exhaust). Only a few bux extra. Don Byrer KJ5KB Radar Tech & Smilin' Commercial Pilot Guy Glider & CFI wannabe kj5kb-at-hotmail.com

"I have slipped the surly bonds of earth; now if I can just land without bending the gear..." "Watch out for those doves..."

Reply to
Don Byrer

Thanks for the suggestions. I read in several other posts that the DPFE may be at fault so I replaced it but unfortunately the problem did not go away. I reset the code (I finally bought an ODB II code reader!) after replacing the DPFE but the code resets after two runs, that is, once the computer completes the EGR valve tests. I?ll look at something else now, perhaps the solenoid?

Reply to
ThomasE

My mom recently traded away her '96 Taurus, but about a year ago she had the same code come up. I replaced the EGR valve (cheapest one was from Ford, verses AZ and O'reillys) and it solved the problem and never came back. I had to somewhat re-route the vacuum line because they had done a revision on the new EGR valve, but I got it to work and we never had anymore problems.

Reply to
Kruse

Well, keep the old DPFE since they do have a high failure rate. At this point you need a vacuum pump and a multimeter to go any further and they're like $30 or more so I think you've done your best for your folks, just tell 'em you tried and to have a Ford mechanic take a look at it. Sorry the new DPFE didn't work for you, I think 99% of the time it does.

Reply to
sleepdog

I looked at the possibility of the solenoid been at fault. To do that, I hooked the vacuum that goes to the solenoid directly to the EGR. I figured that that would cause the EGR valve to be always open (an indeed as I hook up the vacuum to the EGR with the engine running I hear the EGR opening). I cleared the code and drove around twice. I figured that if the solenoid were at fault, I would now get the opposite code, that is, P402=?excessive EGR flow detected? since now the EGR would be always open. However, what I get is the same pending code P0401=?insufficient EGR flow? while the E and C monitor tests were not yet complete after 3 runs ?! and so the check engine light is still off after 3 runs with a pending P0401 code ?!

Reply to
ThomasE

How did the engine run with the EGR fully open? Except at part-throttle cruise, and perhaps not even then, a fully open EGR valve would make the engine run like crap, and almost certainly die at idle. If it indeed was fully open and the exhaust stream gets to the valve, I would suggest that the plumbing from the valve to the intake is clogged. With the plumbing is clogged, no matter where along the way, there will be no pressure drop across the restriction and the DPFE will correctly indicate 'insufficient flow'.

And yes, do get yourself a handheld vacuum pump. You will be wondering how you even managed to do anything around the engine without it.

Reply to
Happy Traveler

Well, the engine was running OK. When I was trying it out hooking the full vacuum to the EGR I did notice some difference in the idling. However I think things are more complicated with these fuel injected engines because the computer compensates for any other stress that you put on the engine and does whatever it needs to do to keep the idle within spec. Even unhooking the vacuum from the solenoid which causes at least some vacuum leak does not seem to affect the idle because I think the computer compensates. besides regarding the EGR exhaust path, when I took the EGR valve out and started the engine, there was quite a bit of noise from the pipes so I believe the EGR plumbing is not clogged, however the thinner bypass lines that go to the DPFE could be clogged, I did not check those.

Reply to
ThomasE

Wiith full vacuum to the EGR at idle the engine should run badly. Sure the computer compensates, but not that much. Need the vacuum pump on the EGR to see if the pintle is opening up enough, could also be clogged or dirty

"Insufficient EGR flow" - If the sensor is good, which you have proven, in English I think this means not enough exhaust pressure drop across the sensor. There's a choke point somewhere (Ok Capt. Obvious), could be clogged intake passages, bad/dirty/tired EGR valve, no vacuum signal to EGR due to broken lines or bad EGR solenoid. If you can get the DPFE tubes off (never did this myself) see if they are clogged, clean them.

Reply to
sleepdog

with the egr off the engine, there should be a rather large vacuum leak too, not just an exhaust leak. Sounds like the intake side might be plugged.

Reply to
ShoeSalesman

Bummer...keep the old one as a spare...as suggested.

The DPFE works on a difference on pressure between two locations. I've seen posts from Ford Owners who found crud (carbon deposits) in the EGR tube that were messing with the DPFE's sensing.

One suggestion is to get a subscription to alldata....that will give you all the t/s ing data and a lot more.

Here's some data for the 99 Taurus Duratec P0401 code

------------------------------------------------------------------------------

The differential pressure feedback EGR sensor and circuit are continuously tested for opens and shorts. The monitor looks for the Differential Pressure Feedback EGR circuit voltage to exceed the maximum or minimum allowable limits. The DTCs associated with this test are DTCs P1400 and P1401.

The EGR flow rate test is performed during a steady state when engine speed and load are moderate and EGR vacuum regulator duty cycle is high. The monitor compares the actual Differential Pressure Feedback EGR circuit voltage to a desired EGR flow voltage for that state to determine if EGR flow rate is acceptable or insufficient. This is a system test and may trigger a DTC for any fault causing the EGR system to fail. The DTC associated with this test is DTC P0401.

--Don Don Byrer KJ5KB Radar Tech & Smilin' Commercial Pilot Guy Glider & CFI wannabe kj5kb-at-hotmail.com

"I have slipped the surly bonds of earth; now if I can just land without bending the gear..." "Watch out for those doves..."

Reply to
Don Byrer

I once again suggest you spend the $$ and get the right data for your car. money well spent on time saved. You obviously have enough smarts to troubleshoot logically... :)

You can get a year of alldata for 12.95, use code:

8001292

How to troubleshoot solenoid on a 99 Taurus:

-----------------------------------------------------------------

Remove the EGR vacuum regulator solenoid. (probly don't need to on this car.) Check EGR vacuum regulator solenoid resistance. Reading must be within

30-36 ohms . Connect vacuum pump to lower port. Block off the upper port and apply vacuum. Check if EGR vacuum regulator solenoid holds vacuum. If resistance reading is out of specification or if EGR vacuum regulator solenoid holds vacuum, replace EGR vacuum regulator solenoid. Install EGR vacuum regulator solenoid.

! Don Byrer KJ5KB Radar Tech & Smilin' Commercial Pilot Guy Glider & CFI wannabe kj5kb-at-hotmail.com

"I have slipped the surly bonds of earth; now if I can just land without bending the gear..." "Watch out for those doves..."

Reply to
Don Byrer

I tested the solenoid. Resistance is 32 Ohms (within spec). I do not have a vacuum hand pump but I can blow through the solenoid with a straw and the air passage is open when there is no voltage applied while the path closes when battery voltage is applied.

But if you don't mind, tell me more about this alldata. It is a service I assume? excuse my ignorance, I'm a novice at troubleshooting cars so it's the first time I hear about alldata. Thanks.

Reply to
ThomasE

formatting link

you can get the factory troubleshooting & repair info online.

I consider it an excellent investment.

check out their sample info..

--Don Don Byrer KJ5KB Radar Tech & Smilin' Commercial Pilot Guy Glider & CFI wannabe kj5kb-at-hotmail.com

"I have slipped the surly bonds of earth; now if I can just land without bending the gear..." "Watch out for those doves..."

Reply to
Don Byrer

As some other responders have suggested, you really should get a hand operated vacuum pump kit. It's very useful for diagnosing vacuum problems. You can even drive the car while controlling the vacuum to the EGR with a long hose connected to the pump. I've done this to diagnose the EGR function at various engine speeds and loads.

Reply to
Fordfan

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