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goldbadgeSat Apr-10-04 01:20 AM
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"Check Engine Light Code Diagnosis"


  

          

Hello everyone,
I'm new to the boards, and to my 1995 Mark VIII, which I just bought with 96,500 miles. It's a nice car that was/is very well kept. I used to be a Auto technician, and did computerized engine diagnosis, but on GM cars. I have an Actron diagnostic scanner and Ford cartridge. The car has a check engine light coming on in cold weather for about the first 5 minutes of running, then it goes off. The car seems to run and drive fine. I ran the KOEO and KOER tests, recorded the codes, then cleared them. Upon checking again, it set a code 326, which is PFE/DPFE EGR sensor below minimum volts. Prior codes were 335-EGR PFE/DPFE volts out of range (KOEO-Slow). Has anyone run into this code, and what was the fix involved? I'm guessing it means replacing the EGR valve and/or sensor if they are not one in the same ? Any guidance on where the valve is on the engine before I go looking ? Any help would be appreciated. I know that a given model tends to have the same failures, and am hoping some here have had this problem. I have a lot of background working on computer related issues so feel free to get as technical as need be.

p.s. Thanks for having a great resource like this on the net for these cars.

1995 Lincoln Mark VIII
148,000k as of 6/10/09

  

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Replies to this topic
Subject Author Message Date ID
RE: Check Engine Light Code Diagnosis
Dec 19th 2002
1
RE: Check Engine Light Code Diagnosis
Dec 29th 2002
2
RE: Check Engine Light Code Diagnosis
Dec 29th 2002
3
RE: Check Engine Light Code Diagnosis
Dec 29th 2002
4
RE: Check Engine Light Code Diagnosis
Dec 29th 2002
5
      RE: Check Engine Light Code Diagnosis
Dec 29th 2002
6
           RE: Check Engine Light Code Diagnosis
Dec 29th 2002
7
           RE: Check Engine Light Code Diagnosis
Dec 29th 2002
8
                RE: Check Engine Light Code Diagnosis
Dec 29th 2002
9
                     RE: Check Engine Light Code Diagnosis
Jan 07th 2003
10

doodaaThu Dec-19-02 12:40 PM
Member since Sep 04th 2002
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#1. "RE: Check Engine Light Code Diagnosis"
In response to Reply # 0
Thu Dec-19-02 12:53 PM

  

          

First off welcome to the board and to the Mark. I'm a noob to both also but I've already learned a couple of things that may help here.

(Sorry Steve I know this is your territory...) Part of having this great resource is the search function. Make sure to check the box to search the archive and you'll likely get quite a few discussions of any problem you can think of.

Sounds like you do need an EGR system checkup and I can't offer much beyond that other than to say I had a similar problem on my '93 Thunderbird a few years back. It's a V6 so it may not be pertinent. I ended up paying for a new EGR valve and a "Throttle Body Cleaning". You may want to look into this cleaning as a diy. There may be some helpful info here http://forums.tccoa.com/showthread.php?s=&threadid=7334&highlight=egr+clean%2A

______________________________

  

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goldbadgeSun Dec-29-02 04:52 AM
Member since Dec 03rd 2002
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#2. "RE: Check Engine Light Code Diagnosis"
In response to Reply # 0


  

          

Anyone else can you comment/help on this issue ?

1995 Lincoln Mark VIII
148,000k as of 6/10/09

  

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teSun Dec-29-02 11:32 AM
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#3. "RE: Check Engine Light Code Diagnosis"
In response to Reply # 2


          

Since this car is new to you, I suggest you disconnect the battery for an hour or so as it acts like reset for the computer and engine idle....Try that and see if it goes away...Make sure to run a decent premium grade gas too....These cars can be virtually tune-up free if you take care of them.

te
94
Gen1
142k miles and counting

  

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drillerSun Dec-29-02 01:49 PM
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#4. "RE: Check Engine Light Code Diagnosis"
In response to Reply # 0


          

I can only chime in on what I've read here, not the personal misfortune of experiencing the problem. IMO, other threads on this board will tell you it is basically a clogged EGR passage. The EGR valve may be just fine, they usually only require cleaning. But the passages are usually clogged w/ carbon, preventing recirculation of the exhaust gases.

As far as location, look at the back of the engine, near the throttle body. Look for a small metal tube coming from the exhaust leading to an emission looking device with a vacumn line attachment. The EGR valve is vacumn controlled via a solenoid valve controlled by the EEC. As a cautionary note, it is a PITA to access. Also the connecting metal tube to the exhaust is quite fragile and even worse to access.

Being an auto tech, you should get a good service manual and EVTM to assist your diagnosis and repairs. Helm is the Ford authorized publisher, www.helminc.com , but good CD versions of the service manual are available also.

Good luck with the Mark VIII, and welcome to the best source for help.



2002 Ford F-250 Super-Duty Powerstroke Diesel Pickup
2000 Mercury Sable LS Premium
1993 Lincoln Mark VIII


  

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goldbadgeSun Dec-29-02 02:17 PM
Member since Dec 03rd 2002
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#5. "RE: Check Engine Light Code Diagnosis"
In response to Reply # 4


  

          

The engine doesn't ping at all, and I didn't think it was clogged because the error code indicates an EGR SENSOR voltage is out of range, nothing was indicated as far as blockage or flow. Does this EGR sensor measure movement of the EGR pintle valve or maybe exhaust flow? I just wanted to know if anyone knew if the sensor was part of the valve, or could be replaced seperate etc, and any other advice on this subject. Thanks, Kurt

1995 Lincoln Mark VIII
148,000k as of 6/10/09

  

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magic_markerSun Dec-29-02 04:37 PM
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#6. "RE: Check Engine Light Code Diagnosis"
In response to Reply # 5
Sun Dec-29-02 04:46 PM

          

Goldbadge - The DPFE sensor is NOT part of the EGR valve - Here's what I found using the service manual CD:

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

Remember:

To prevent the replacement of good components, be aware that the following non-EEC areas may be at fault:

l Damaged EGR valve

l Restricted exhaust

l Damaged vacuum reservoir

This Pinpoint Test is intended to diagnose only the following:

l Harness circuits: VREF, DPFE, SIG RTN, EVR, VPWR

l PFE sensor (9D460)

l EVR solenoid (9J459)

l Powertrain Control Module (PCM) (12A650)

l DPFE sensor (9J460)

l EGR valve assembly

l Vacuum lines (EVR, PFE/DPFE)

l DPFE Sensor Pressure Hoses


Description

The Pressure Feedback Electronic (PFE) EGR system consists of a pressure sensor (PFE sensor), Electronic Vacuum Regulator (EVR) solenoid, and a vacuum actuated EGR valve. The Differential Pressure Feedback Electronic (DPFE) EGR system uses a differential pressure sensor (DPFE sensor) that has two pressure inlets. The PFE system has one pressure inlet in the sensor.

In both systems, the EVR solenoid regulates a vacuum signal to the EGR valve in response to a duty cycle signal from the Powertrain Control Module (PCM). The EVR solenoid will vent some of the source vacuum and transmit the remaining vacuum to the EGR valve in response to the level of the duty cycle. The higher the duty cycle, the more vacuum transmitted to the EGR valve. Due to the design of the EVR solenoid, the vacuum at the EGR valve never reaches the source vacuum level.

EGR flow rate is determined by monitoring the pressure across a fixed metering orifice as exhaust gasses pass through it. The DPFE system monitors this flow across the orifice by supplying the DPFE sensor with a pressure signal before the orifice (upstream pressure) and a pressure signal after the orifice (downstream pressure). The DPFE sensor then evaluates these two pressure inputs and determines the pressure difference across the orifice. This pressure difference translates to a specific EGR flow which the DPFE sensor signals the PCM by an analog voltage signal. This signal to the PCM increases linearly as the differential pressure increases. The PFE system, unlike the DPFE system, has only one pressure signal input (downstream) and must rely on the PCM to indirectly infer the upstream exhaust pressure in order to determine the EGR flow rate. The PFE sensor transmits an analog voltage signal which decreases linearly as EGR flow increases.

The PCM optimizes the EGR flow rate by varying the EVR duty cycle using the feedback signal the PFE or DPFE sensors provide.
-------------------------------------------------------------------
Here is diagnostic info for your 326 code...
-------------------------------------------------------------------


DTC 326 or 327 indicates the DPFE circuit voltage is lower than expected at zero duty cycle.

l Key off.

l Check PFE/DPFE sensor pressure input hose(s) for obstruction and/or leaks.

l Are there any obstructions or leaks?

Yes
SERVICE as necessary. RECONNECT all lines. RERUN «Quick Test».

No
GO to «DL23»...

DL23 CHECK PFE/DPFE SIGNAL VOLTAGE WITH ENGINE AT IDLE

l Key off.

l Disconnect Powertrain Control Module (PCM). Inspect for damaged or pushed out pins, corrosion, loose wires, etc. Service as necessary.

l Install breakout box and connect PCM to breakout box.

l Start engine and idle with transmission in PARK or NEUTRAL.

l Measure voltage between Test Pin 27 and Test Pin 46 at the breakout box.

l Is voltage less than 2.9 volts (PFE) or 0.2 volt (DPFE)?

Yes
For DPFE Applications:
REPLACE DPFE sensor. REMOVE breakout box. RECONNECT all components. RERUN «Quick Test».
For PFE Applications:
GO to «DL24».

No
REPLACE PCM. REMOVE breakout box. RECONNECT all components. RERUN «Quick Test».
--------------------------------------------------------------------
Diagram of DPFE system
-------------------------------------------------------------------



Hope this helps!

-Scott

  

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logresSun Dec-29-02 05:55 PM
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#7. "RE: Check Engine Light Code Diagnosis"
In response to Reply # 6


          

www.jcwhitney.com sells a catalytic converter/EGR/oxygen sensor cleaner for $10. It's a liquid you put in the gas tank. There was no way for me to verify it was actually working, but for $10, it's better than replacing parts. And for what it's worth, I did notice a positive difference.

If that doesn't work, I've found that EGRs are all fairly simple devices. I had an 85 T-Bird where I took off the EGR as part of some other repair job and found the breather holes to be about 50% closed with carbon. You can scrape off the carbon with a handy screwdriver and then reinstall it. On our cars, the EGR is fairly easy to get at. It is up against the driver side firewall.

93 Mark VIII "Defiant"
"Do not despair; but if you must, fight on in despair."

  

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goldbadgeSun Dec-29-02 07:45 PM
Member since Dec 03rd 2002
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#8. "RE: Check Engine Light Code Diagnosis"
In response to Reply # 6


  

          

Scott, thank you for the wealth of information. I will be able to go from here and have a better chance of fixing this issue. Now to go out and find the DPFE sensor. My bet is that its gonna be bad or something is up with the orifice. Thanks again, Kurt

1995 Lincoln Mark VIII
148,000k as of 6/10/09

  

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magic_markerSun Dec-29-02 07:56 PM
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#9. "RE: Check Engine Light Code Diagnosis"
In response to Reply # 8


          

Kurt, no problem!

Also, check these links out - they're worth a look:

http://www.autotune.com/techtips/at_sen.html

http://www.cybrrpartspro.com/Chilton%20Manuals/9117m/9117CH04_13.HTML

http://www.obdiicsu.com/Studies/1999CaseStudies/study.html

http://www.suitorsgarage.com/projectstaurus1.html

  

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RoadieTue Jan-07-03 08:59 PM
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#10. "RE: Check Engine Light Code Diagnosis"
In response to Reply # 9


          

I was getting an egr code and took it to the dealer expecting a new egr valve. The mechanic cleaned a groove that I believe he said was at the base of the throttle body and replaced the flow sensor. I also was told by my nephew mechanic that he replaced everything on a crown vic and still did not fix the problem until he found out about this groove that clogs up with carbon or something. Check this out before you replace the egr. They are a real pita to get to and replace. I know because I tried before I took it to the dealer. I was only home for a weekend and I gave up.

Roadie
2005 Dodge Magnum
86 Monte Carlo SS (Wife has the new)
81 Honda CB900C (SUV, of course)

  

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