P0401 and EVAP

[DRW1000]

Hi Everyone,

I was about to do the intake manifold vacuun leak on my 99 Windstar as I assumed this was the reason for my CEL. I never checked the codes because it costs a minimum of $50 CDN to have them read up here in Canada as we do not have Autozones and I assumed the vacuum leak was highly likely. I decided to buy a code reader as I assumed it would pay for itself over time. (It already has in my opinion)

I was surprised to discover that when i read my codes I got P0401 which is "insufficient EGR flow". It also registere the the EVAP circuit has not had the proper OBD2 drive cycles to have completed this test. (I erased my codes last week using the battery disconnect method).

I have 2 questions for anyone who may have an idea.

P0401- I assume that this could be due to clogged EGR ports that will require that I either remove the upper intake manifold cover for access or I spray something throught the egr valve port to clear it up. I would try seafoam but it is not available up here. We have a product called "Guaranteed to pass" that the guy in the store told me would clear up the ports but I wasn't sure since it goes in the gas. He seemd to think it would burn and eventually go through the EGR ports but I feel the concentration would then be too weak to really do anything. Does anyone else have any ideas?

EVAP- Does anyone know what type of drive cycles I need to take the vehicle on to have the PCM test this sensor. At first I thought it may be a bad circuit and thus unable to test but it looks like there is a code for the EVAP circuit failure (P0443) Again and ideas are welcomed.

Thanks to everyone

[rodeo02]

1) I've never seen a fuel tank additive capable of clearing out clogged EGR plumbing. Some fuel system additives will reduce carbon build-up, but once the additive is combusted in the engine, it looses most of it's cleaning ability. Seafoam is good stuff, but a cheap $1/can spray carb/intake cleaner will work just as well if you have the EGR valve removed.

2) I dont know the number of drive cycles needed to clear that EVAP system malfunction code, but is usually quite high, like 25-100 full warm-up & drive cycles. This could be just a stuck check valve in the gas cap allowing tank press to bleed off. Make sure you can just suck air thu and not blow air out of the gas cap (neighbors love this maneuver). Does the '99 have a check gas cap light? (a little gas cap icon).

G/luck
Joel

[DRW1000]

Hi Rodeo,

1) Yeah I am going to try and take the EGR off to do so.
2) Actually from what I understand there is no malfunction in this instance. I cleared the codes last week and I have not had the proper drive cycle(s) to get the system tested. I do not have the gas cap icon (at least I have never had it go on if I do)

[DRW1000]

Well I started to troubleshoot my EGR system. The first thing I did was remove the vacuum to the EGR valve and while the vehicle was idling I applied vacuum to the EGR valve and the car stalled. For the time being I am assuming that the EGR valve works and the ports are relatively clear.

I then wanted to check the EVR but it was at the back of the engine and it was cold so I moved on.

I started to look at the DPFE. I am no too sure how this sensor works but I think if it senses a difference in pressure from it's two inputs then this would indicate that the EGR valve is opened. If the sensor detects equal pressure then the valve is close (so I believe).

At cold it should read less than 1 volt and between 4 and 6 volts at hot. (this is from my Haynes)

For some reason mine reads about 4.67 volts at cold and remains that way. I was not able to take it for a drive to fully warm up but I did let it warm up in the driveway and it never changed.

I then thought that perhaps it is seeing a pressure difference at cold. It does not make sense since the engine idles nicely.

As an experiment I disconnected the two exhaust inputs and measured the signal voltage. Again it read 4.67 volts. I assumed that this is equal pressure on both inputs (atmospheric) and should be the equivalent to no flow through the EGR.

I am almost positve this sensor is malfunctioning but I wanted someone else to review and comment on my logic.

Thanks

[rodeo02]

Sounds like some good troubleshooting on your part . Given that your van stalled out at idle when you manually pulled a vacuum on the EGR valve sounds like the EGR is flowing adequately & the valve works. Look into that differential pressure switch for the EGR further. Maybe you can remove & clean it with some degreaser or electronics cleaner. G/luck & keep us posted!
Joel

[DRW1000]

Thanks Rodeo,

I looked into it a bit more. I hooked up a voltmeter on the DFPE (signal to ground) I get a constant 4.67 V. I then using human power created a vacuum on the input to the EGR. The engine started running rough and I held the vacuum and watched the meter. It never changed. I released andthe engine started running smooth. I cleaned the Sensor and the lines from the Exhaust and tried again. Again no change. I felt the exhaust to the EGR and it was getting hot so flow is occuring.

I then stalled the engine and using human power I heard the EGR opening and closing.

Almost ready to buy new DFPE.

2nd issue
I can't seem the get my EVAP system to complete it's test. I would have thought it would have by now.

[DRW1000]

Well I thought I would provide some feedback.
1) I bought a used DPFE form a junkyard but it was from a Contour. I did not want to use it since I did not know the internal differences and I did not want to risk damage to my PCM. I did however drill out the rivets to have a look and I bench tested it to see what makes it tick. I then opened up my old one and with a voltmeter I determined that from the external contacts to the inside PC board was a break in one of the wires. I used the case form the contour one (of which the break was potted) and transferred the guts of my old one and put it together. Now I get voltage changes that track the EGR valve opening. The only trouble is my idle voltage is 2.5 volts but it does go up smoothly with EGR to 4.7 volts. I removed both inputs to see if the EGR was stuck aand no change. The good news is ny CEL is off. I also noticed that the new plastic DPFEs at idle are 1.0 volts and not the 0.2 that the old ones were. What the threshold is for a failure is anybody's guess. I also have no codes.

2) Evidently the EVAP monitor is the hardest monitor to run. You only have 30 minutes from an 8 hour cold soak. I have a very hard time getting to a highway in under 30 minutes. Plus the air temperature has to be above 4.4 celcius. This is now possible as it is warming up here but mornings can still be cold.

[ModMech]

DRW,

You have done an excellant job of troubleshooting. You don't have to worry about EEC damage from different DPFE sensors, they all work in the same way, only the relative calibrations are slightly different.

Also, you cannot clear codes on an EEC-V ('96 up) vehicle by removing the battery connection(s), even if for days. The ONLY way to clear them is with a scan tool/code reader. All you accomplish by disconnecting the battery is to lose the Keep Alive Memory (KAM) which is the "learned" adaptive memory of the EEC.

[DRW1000]

Hi ModMech,

Are you sure about the relative calibrations? I have since learned from a Ford dealer that the new F77Z-9J460 replaces both the F7uE (from my windstar) and the F48E (from the contour) but I did not trust the guy because I think I was annoying him with my questions. I would like to try the F48E (from the contour) as I think it bench tested down to 0.2 volts with no pressure. So are you totally sure? I am so close to trying it.

I used a code reader to erase my codes

[DRW1000]

One other question. IF I have no codes does this mean that my car "thinks" it does not have an emissions problem and I should feel confident in getting it tested. ( I suppose I could ask it another way: If I have an emissions problem will my CEL come on?)

[ModMech]

The CEL WILL positively illuminate IF you have an emissions problem. Does that mean the vehicle will pass? Not exactly. Some areas test for tailpie only (PASS), tailpipe and CEL (PASS), or tailpipe, CEL, and drive cycle (fail). So it depends on what type of inspection you are subject to.

As for the DPFE sensors, I can't say one will work OK, only that it will not damage the EEC.

[DRW1000]

Thank you ModMech. I understand what you mean. I don't know if it will work but at least I can try it without fear of damage.

I wasn't sure what you meant by "tailpipe, CEL and drive cycle (fail)". Actually it is the fail in brakets that is confusing me.

[ModMech]

When you clear the codes, OR dump the KAM the drive cycle evap, cat efficiency and other tests need a number of "cycles" and "key on/offs" to complete the test regimine.

[DRW1000]

Yes that I am aware of as I had a hard time getting my EVAP monitor to run.

What I was unsure of is what did you mean by the (fail) in the brakets.

I have fixed a problem on my car and I cleared the codes with my code reader. I have driven it and managed to get all of the monitors to run. I do not have my CEL, do not have any pending codes. So perhaps I should have asked the question this way.

" My sensors are not picking up anything that is causing my PCM to set a code. (not even a pending one). All of the monitors have run their tests and my CEL is off. Does this mean that as far as my car is concerned it is not creating excessive emissions and is my car "smart" or sensitive enough to know that it is compliant and can pass the test".

I hop I have asked this clearly.

[ModMech]

If all the monitors have been completed, than it should pass. One of the biggest reason for a fail is a recent code retrieval and clearing (or even a battery replacement) that dumps the KAM and monitors. That's whay I wrote (fail) because the monitors can take a week to complete if you don't drive often or far.