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Discussion Starter · #1 ·
First off I have a 1999 3.0 Bull. Being this is my first post hopefully everything goes right. My check engine light started flashing today which I know means a misfire. Went to AutoZone and ran the code and there were 4 of them; P0401 and P0301/3/5. I know what the codes mean, I guess I just need help in troubleshooting the issues.

About 11 months ago I got the same misfire codes and took the car in for a tune up and had the plugs and wires replaced. The car is ideling pretty rough and you can tell there is a misfire. Could the EGR code be causing the misfire? Any suggestion would be apperciated....Thanks in advance
 

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Prob. need new dpfe (egr pressure sensor) for 401 code. If plugs and wires are fairly new, i would replace the coil. Az can do a primary and secondary resistance test on your old coil, or you can if you have an ohmmeter and a manual. Imho, test is mostly a waste of time because they can test in spec. and so many times fail under load. With coil off car, carefully check it for cracks (esp. on the bottom), corrosion and general overall damage. Then prob. replace it. 401 code is not causing your misfire.
 

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P0401
EGR Flow Insufficient Detected​
Detailed DescriptionThe EGR system is monitored during steady state driving conditions while the EGR is commanded on. The test fails when the signal from the DPF EGR sensor indicates that EGR flow is less than the desired minimum.
Possible causes :-<LI class=bodyText>Vacuum supply. <LI class=bodyText>EGR valve stuck closed. <LI class=bodyText>EGR valve leaks vacuum. <LI class=bodyText>EGR flow path restricted. <LI class=bodyText>EGRVR circuit shorted to PWR. <LI class=bodyText>VREF open to DPF EGR sensor. <LI class=bodyText>DPF EGR sensor downstream hose off or plugged. <LI class=bodyText>EGRVR circuit open to PCM. <LI class=bodyText>VPWR open to EGRVR solenoid. <LI class=bodyText>DPF EGR sensor hoses both off. <LI class=bodyText>DPF EGR sensor hoses reversed. <LI class=bodyText>Damaged EGR orifice tube. <LI class=bodyText>Damaged EGRVR solenoid. <LI class=bodyText>Damaged PCM.
Diagnostic AidsPerform KOER self-test and look for DTC P1408 as an indication of a hard fault. If P1408 is not present, look for contamination, restrictions, leaks, and intermittents.



I would give it a good "once over" just to be sure the vacuum lines are not cracked, leaking, loose, etc. Maybe even pull the EGR valve off and see if its all gunk-a-fied. Remember, lather, rinse repeat. Always repeat...
 

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You can easily test egr valve itself on the car with eng. idling. Pull off vac. hose and replace it with a pc. of scrap test hose. Suck on test hose. Eng. should stumble or die meaning valve is working. Remember, there should be no egr flow @ idle or wot (wide open throttle).
 

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Discussion Starter · #6 ·
You can easily test egr valve itself on the car with eng. idling. Pull off vac. hose and replace it with a pc. of scrap test hose. Suck on test hose. Eng. should stumble or die meaning valve is working. Remember, there should be no egr flow @ idle or wot (wide open throttle).

Thanks for all the great info. Just have a few further questions. The EGR valve the little cymbial shaped deal and the DPFE is the little box on the passenger side near the fire wall with the little hose's?
 

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If it's P0401 then you have a low-flow only code. More often than not that requires cleaning the throttle body and upper intake EGR passages. They're plugged with carbon usually, and on an 11 year old Taurus that's likely the problem. If you've never replaced intake gaskets and PCV hoses, it's a good idea to knock it out all at once. The gaskets and hoses aren't expensive, but the labor to keep pulling things apart and fixing individual problems is.
 

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The P0401 is usually the Pressure Feedback sensor (DPFE). For the misfire, I'd check the ignition coil for cracks or pull the wires off one by one while the engine is running to check for sparks (usually done at night)... If not, you could have a bad plug or bad wires, which is possible. After 12K miles on brand new wires, I developed in idle-only misfire and finally determined it was the wires. Changed them and the car runs very smoothly.

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Yes, you have identified them correctly. If you replace the dpfe sensor and coil, i would recommend you buy the borg-warner(bwd) units from adv. auto or oreilly. Ive had numerous probs. with az sensors and coils in the past.
 

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I would correct the misfire pretty quickly because with a flashing lt. misfire you are prob. dumping unburned fuel down into the cats which can destroy them.
 

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Discussion Starter · #11 ·
The P0401 is usually the Pressure Feedback sensor (DPFE). For the misfire, I'd check the ignition coil for cracks or pull the wires off one by one while the engine is running to check for sparks (usually done at night)... If not, you could have a bad plug or bad wires, which is possible. After 12K miles on brand new wires, I developed in idle-only misfire and finally determined it was the wires. Changed them and the car runs very smoothly.

I'll give this a try tonight after work. When you say pull the wire off do you mean from the coil or off the the individual plugs? This may sound stupid, but I want to see sparks right?
 

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I'll give this a try tonight after work. When you say pull the wire off do you mean from the coil or off the the individual plugs? This may sound stupid, but I want to see sparks right?
No, that was bad advice to be blunt. Yanking a plug wire off with the car running won't do anything except verify that getting shocked hurts. If you want to check spark, buy a spark tester that connects between the plug boot and plug. There are gap and lighted spark testers. Or buy a noid light to verify signal to the injector. Or just remove the #1 plug and examine it for flooding. Or swap plugs and wires and see if the miss follows the #1 plug/wire.

The car has already told you there's a #1 misfire by way of its power balance test. You're just trying to determine now if it's spark or fuel.
 

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Discussion Starter · #13 ·
No, that was bad advice to be blunt. Yanking a plug wire off with the car running won't do anything except verify that getting shocked hurts. If you want to check spark, buy a spark tester that connects between the plug boot and plug. There are gap and lighted spark testers. Or buy a noid light to verify signal to the injector. Or just remove the #1 plug and examine it for flooding. Or swap plugs and wires and see if the miss follows the #1 plug/wire.

The car has already told you there's a #1 misfire by way of its power balance test. You're just trying to determine now if it's spark or fuel.

Cool. I bought a spark tester and gonna start this weekend. Hopefully it's a easy fix. I'm going to assume if the spark is good then it may be the injectors
 
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