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Discussion Starter · #1 ·
Kalifornia Disclaimer: This disables your EGR valve which is a component of your emissions system and something called the Air Research Board seems to think it is critical to fuzzy little animals that it functions, even though it is only active at idle and cruising RPM. Disabling the EGR system has been known to cause cancer in the state of California.

Now with the legal mumbo jumbo out of the way, let's lay out the facts of this modification:

- Ford's DPFE, Differential Pressure Feedback EGR, system is incredibly flawed. It takes pressure sampling prior and post an orifice in the EGR sampling tube to ensure the EGR valve is properly functioning. However, this pressure sampling involves introducing hot exhaust gas into the DPFE sensor. If engine temperatures were to spike, from a cooling system failure or even just a cylinder misfire, there is a probability for the sensor to melt:



The other downside for introducing exhaust gas into the DPFE sensor is that the combustion cycle is not perfect, you have carbon present in the exhaust. This is the primary killer of the DPFE sensors. If this is the culprit of the failure, and you do not replace the rubber hoses and clean the sampling tube, you will experience another DPFE failure in short order.

So this modification will help save you from buying a DPFE sensor ever again (Usually a $40 or $50 investment).

- Again, the EGR valve only functions at idle and cruising engine speeds, for most people, the EGR valve is rarely operating given their driving habits.

- This modification keeps the EGR valve and DPFE sensor in place. The DPFE sensor will continue to report proper operation of the EGR valve, so it will pass an inspection via computer. With a little thought, it will also pass a visual inspection.

Steps:
1. Open hood, locate your EGR valve and DPFE sensor, on my G4.5 Vulcan, it was located dead center on the back of the intake manifold.
2. Disconnect both hoses from the DPFE, plug these hoses with something (The one million hex keys I have laying around always work good for this) or remove the hoses and cap the metal nipples with something that can withstand heat and exhaust gas.
3. Disconnect vacuum line from the top of the EGR valve and connect it to the REF (Reference) side of the DPFE sensor, if like in my case and you can't see the markings on the sensor, the REF side is the smaller nipple and obviously the only one the EGR vacuum line will fit on.
4. You are done, besides a little cosmetic tomfoolery of putting a vacuum line back on the EGR valve and tucking it behind the motor, so it looks like it is connected. Same with the larger nipple on the DPFE sensor, if you feel it is necessary, slip a hose on it that leads nowhere.

With this setup, the DPFE sensor still sends the proper signal, it still thinks it is hooked up. On the REF side, it is pulling full manifold vacuum, which is variable and the other side pulls from the atmosphere which is constant.

So what are the benefits of this bypass?

- Possibility of a slight mileage increase. Preliminary reports from Ranger Power Station say they noticed their gas mileage increase slightly.

- Bottom end seems to have a bit more punch and a bit more responsive.

- And as already stated, no more DPFE sensor replacements.

So far I have put about 25 miles in with the EGR bypassed, no Check Engine Light, all readiness monitors are active.
 

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Your details of the DPFE are a bit flawed... There is a membrane between the two ports of the sensor. Deformation of the membrane, caused by pressure differential (hence the name) between the ports is translated into a variable signal reported to the computer. This is why it's connected on either side of the orifice. With a good sensor, there is no gas flow thru it and therefore no hot exhaust reaches it.

The original vacuum line to the valve is controlled by the EVR, and there is no vacuum supplied at idle. The EGR is only active during part throttle cruise conditions.

As far as increase in mileage/power, it certainly is possible. You are removing the inert exhaust that is diluting the fuel mixture and you get more power per combustion cycle.
 

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This may cause pinging as the exhaust gas retards combustion. The ignition timing curve is based on functioning EGR, so it may be too advanced during cruise.
 

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This may cause pinging as the exhaust gas retards combustion. The ignition timing curve is based on functioning EGR, so it may be too advanced during cruise.
Definitely something to consider.

84FordMan, I don't know what grade gasoline you use, but if you could run it through a test of cruise & WOT on a flat road, then cruise (or ~2k RPM) & WOT up a steep incline with 87 octane without any pinging problems, then I'll definitely do that mod.
 

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Pinging should not be an issue here, as the mod is designed to eliminate introduction of exhaust gas into the combustion chamber. WOT and other conditions demanding more power turn off the EGR system by design anyway.
 

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Discussion Starter · #8 ·
I run only 87 in the Taurus, however, in my other Vulcan powered vehicle, the 94 B3000, it won't see anything less than 89 due to pinging (Even with a functional EGR system) due to the carbon harvesting heads. I've never had that problem in the Taurus, so I am wondering if Ford finally addressed that issue when they changed head castings in the late 90s.

I will check the cruise conditions in a bit.
 

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The carbon deposits that allegedly form to plug the EGR ports only forms if the vehicle is running rich. This is usually because the O2 sensors have not been replaced at the scheduled maintenance interval of between 60,000 - 80,000 miles. If you replace the sensors, it prevents the rich conditions that promote the formation of carbon deposits.

As far as improving gas mileage, its possible. But you have to realize, the inert gas does not change the fuel to air ratio, because technically the fuel to air ratio is actually the fuel to oxygen ratio, which remains relatively unchanged. One would have to question, if the EGR failed due to a rich condition, then does the fuel economy really increase because the EGR was bypassed, or because the act of bypassing it acts as a band aid to the real problem that caused the EGR failure to begin with?
 

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The carbon deposits that allegedly form to plug the EGR ports only forms if the vehicle is running rich. This is usually because the O2 sensors have not been replaced at the scheduled maintenance interval of between 60,000 - 80,000 miles. If you replace the sensors, it prevents the rich conditions that promote the formation of carbon deposits.

As far as improving gas mileage, its possible. But you have to realize, the inert gas does not change the fuel to air ratio, because technically the fuel to air ratio is actually the fuel to oxygen ratio, which remains relatively unchanged. One would have to question, if the EGR failed due to a rich condition, then does the fuel economy really increase because the EGR was bypassed, or because the act of bypassing it acts as a band aid to the real problem that caused the EGR failure to begin with?
The mileage increase could be seen as a change in driver behavior from the increased responsiveness of the engine. If you had more power, but didn't know it, you would use less throttle to maintain the same driving habits. Less RPM = less fuel consumed. While it may consume more fuel because it's packing more fuel/air into the cylinders, it will do it less often.

This is also just a theory. Don't attack me because your high-school science teacher told you different.
 

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Discussion Starter · #11 ·
And on the 3rd day, God said let their be a Check Engine Light. I tested extensively at idle, cruise and WOT runs all over the map. In the first two days, I put over 40 miles on the car and no issues. Now there is a DTC and care to guess what it is? EGR Insufficient Flow, directly relating to the DPFE. I also got some interesting freeze frame data, which I will get to in a second, but first.. I cleared the code. Drove it again and in less than 13 miles it came back. I am stumped by this, when I did this modification at first, all the readiness monitors were active and reporting fine.

Anyway, to the data from the freeze frame, the fuel trims caught my attention:

STFT B1 -2.3
STFT B2 -2.3
LTFT B1 1.5
LTFT B2 2.3
RPM 2,038

So there is your proof on fuel economy. Disabling the EGR caused it to run rich and the ECU is taking away fuel. With time the LTFT B2 will be 0 :lol2:. What concerns me is in the LTFTs, there is an imbalance between the banks, while only .8, still, it gives me flashbacks to my Mazda6 which had a factory imbalance in the LTFTs and come to find out the EGR sampling tube protruded into the intake manifold and blocked off a good portion of the rear bank. Cutting 2" out of the tube balanced out the LTFTs.

I am going to check and make sure the vacuum line to the REF side hasn't vibrated off.
 

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Discussion Starter · #13 ·
Found the cause of the problem, the 90-degree boot that is apart of that vacuum line (That used to go to the EGR valve) has split. The slightest little tap on the line and the boot fell off the DPFE REF nipple.
 

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The DPFE was probably not designed to withstand full manifold vacuum. It could have been damaged.
That part is true...It's a differential sensor, and at idle the difference is about 20". PCM thinks max EGR is flowing, when it should not be. Expect to see a code for excessive flow next.
 

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And on the 3rd day, God said let their be a Check Engine Light. I tested extensively at idle, cruise and WOT runs all over the map. In the first two days, I put over 40 miles on the car and no issues. Now there is a DTC and care to guess what it is? EGR Insufficient Flow, directly relating to the DPFE. I also got some interesting freeze frame data, which I will get to in a second, but first.. I cleared the code. Drove it again and in less than 13 miles it came back. I am stumped by this, when I did this modification at first, all the readiness monitors were active and reporting fine.

Anyway, to the data from the freeze frame, the fuel trims caught my attention:

STFT B1 -2.3
STFT B2 -2.3
LTFT B1 1.5
LTFT B2 2.3
RPM 2,038

So there is your proof on fuel economy. Disabling the EGR caused it to run rich and the ECU is taking away fuel. With time the LTFT B2 will be 0 :lol2:. What concerns me is in the LTFTs, there is an imbalance between the banks, while only .8, still, it gives me flashbacks to my Mazda6 which had a factory imbalance in the LTFTs and come to find out the EGR sampling tube protruded into the intake manifold and blocked off a good portion of the rear bank. Cutting 2" out of the tube balanced out the LTFTs.

I am going to check and make sure the vacuum line to the REF side hasn't vibrated off.
I don't entirely follow. So disabling the EGR is leaning it out over time, after a sudden increase in richness? Will it not just lean out to the A/F ratio it had with EGR?
 

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Discussion Starter · #16 ·
I don't entirely follow. So disabling the EGR is leaning it out over time, after a sudden increase in richness? Will it not just lean out to the A/F ratio it had with EGR?
With the EGR enabled, it was adding fuel over factory. Without the EGR, it's now cutting fuel. Don't think of it as running rich or leaning out.

Over time the ECU will record the STFT and take the difference from the LTFT. The oxygen sensors will no longer see there is a difference. You don't want the ECU cutting or adding fuel in compensation over preset fuel trims.
 

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- Again, the EGR valve only functions at idle and cruising engine speeds, for most people, the EGR valve is rarely operating given their driving habits.
Not sure where you're getting this data from, but the EGR does not operate at idle, and usually not above moderate acceleration. Even if you're accelerating at a decent rate, the PCM is calling for some EGR and commanding the PWM control solenoid to open.

So you can either hackjob the EGR system....
Or.. You can just pull up the fuel trims and lean them out a bit and set the EGR request to 0 across the entire map and get the same effect without hacking and bypassing system sensors;)
 

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Discussion Starter · #18 ·
So you can either hackjob the EGR system....
Or.. You can just pull up the fuel trims and lean them out a bit and set the EGR request to 0 across the entire map and get the same effect without hacking and bypassing system sensors;)
Proper way? Definitely, but I sought out an alternative, 'hackjob', due to the fact I don't have an SCT and doesn't appear I will be able to get one anytime soon.
 

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Discussion Starter · #19 ·
Fixed the vacuum leak and after a drive cycle, the code has cleared itself out.
 

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Discussion Starter · #20 ·
Update, still no codes, driven daily 50 miles round trip. Decided to go ahead and clean-up some more of the mess from the EGR system. I removed the sampling pipe.. in two pieces:



Very brittle piece, didn't show any signs of rusting or pitting, so, just cheap metal. I was trying to break free the nut on the manifold side while holding the EGR tube with my bare hand and pop. Lucky where it broke too, made it even easier to remove.

Had the parts store bring in a replacement manifold and I asked for the nut that it ships with, seeing as everyone would remove it and just throw it away when installing the EGR tube. Made the rest of the transition go real smooth:



EGR valve is still bolted to the intake manifold, this is no problem as when no vacuum is applied to the valve, it stays air-tight shut. Will remove a little later on, I ordered a shiny EGR block-off plate from UPR, it is designed for 4.6L Mustangs, but will work just fine as the 3.0 and 4.6 use the same EGR valve gasket.

Allowed the engine to warm up on its own from idling. No lights or codes. Was a minor exhaust leak from the nut, retightened it and it's gone.
 
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