How To: Bypass EGR without getting a CEL


adsm08

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The limp mode you are talking about just pretty much bypasses everything doesn't it? As in the EGR doesn't work, it don't shut down the fuel injectors when coasting, etc.? It also effects timing advance and that type of stuff as well correct?
I don't know exactly what all is effected. I believe the EGR is shut down. I know the air-fuel calculation goes to pre-set values and the oxygen sensors are basically ignored.
 


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wildbill23c

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I don't know exactly what all is effected. I believe the EGR is shut down. I know the air-fuel calculation goes to pre-set values and the oxygen sensors are basically ignored.
Disconnected the EGR switch this afternoon, drove it again, same power loss going up the same hill. Only seems to do it when under moderate to heavy acceleration. With the EGR switch disconnected and pulling the vacuum hose off from the EGR sensor side under the throttle linkage plate I'm getting pulsating air out of that hose, I'd think the EGR valve being disconnected it would be closed and no air would be escaping through that hose?
 

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I didnt read this whole thing but theres been a few anti EGR posts lately. The system is cheap and easy to fix... why do you try to delete it?

But to answer you wildbil, it "should" be closed and only open at steady cruise but if the valve is cruddy it will stick partially open even with the dpfe disconnected which is not good for heavy engine load.
 

adsm08

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Disconnected the EGR switch this afternoon, drove it again, same power loss going up the same hill. Only seems to do it when under moderate to heavy acceleration. With the EGR switch disconnected and pulling the vacuum hose off from the EGR sensor side under the throttle linkage plate I'm getting pulsating air out of that hose, I'd think the EGR valve being disconnected it would be closed and no air would be escaping through that hose?
It's been a long time since I worked on a 2.9 hands on, and even longer since I worked on one with EGR. But if you pulled the line to the sensor off it should have exhaust coming out. That's an EGR flow sensor, which operates a little differently than a DPFE, but with the same basic principal. It monitors the pressure in the EGR tube, and infers the amount the valve is open based on pressure in the tube. So yes, the line to the sensor should have exhaust coming out even if the valve is closed.

A DPFE makes it's inference based on a pressure differential across a calibrated orifice. There is a piece in a DPFE EGR tube inside between the two sensor tubes with a smaller hole in it to create a restriction. The DPFE sensor can detect the different pressures on either side and calculate the percentage of the valve being open based on that.
 

wildbill23c

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It's been a long time since I worked on a 2.9 hands on, and even longer since I worked on one with EGR. But if you pulled the line to the sensor off it should have exhaust coming out. That's an EGR flow sensor, which operates a little differently than a DPFE, but with the same basic principal. It monitors the pressure in the EGR tube, and infers the amount the valve is open based on pressure in the tube. So yes, the line to the sensor should have exhaust coming out even if the valve is closed.

A DPFE makes it's inference based on a pressure differential across a calibrated orifice. There is a piece in a DPFE EGR tube inside between the two sensor tubes with a smaller hole in it to create a restriction. The DPFE sensor can detect the different pressures on either side and calculate the percentage of the valve being open based on that.
Dang, the EGR valve is NOT the problem. The problem was the brand new fuel pressure regulator is bad. I borrowed a fuel pressure tester, at idle I got 28psi, if I revved the engine the fuel pressure was dropping to about 10-15psi. I'll be replacing that fuel pressure regulator. Ugg, although at least I now know its something simple not a electrical or computer issue.

Thank you adsm08 so much for your help. I really appreciate it.
 

adsm08

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Dang, the EGR valve is NOT the problem. The problem was the brand new fuel pressure regulator is bad. I borrowed a fuel pressure tester, at idle I got 28psi, if I revved the engine the fuel pressure was dropping to about 10-15psi. I'll be replacing that fuel pressure regulator. Ugg, although at least I now know its something simple not a electrical or computer issue.

Thank you adsm08 so much for your help. I really appreciate it.
I would pop the vacuum line off the regulator and see what happens before replacing it. Low pressure at idle that goes down off idle can also be a failing fuel pump. If the pressure at idle spikes back up to where it should be, or at least climbs, with the vacuum line disconnected then the regulator is likely at fault. If it stays the same I'd look at the fuel pump first.

At least if it's the pump you are looking at the external high pressure pump and not the one in the tank.
 

wildbill23c

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I would pop the vacuum line off the regulator and see what happens before replacing it. Low pressure at idle that goes down off idle can also be a failing fuel pump. If the pressure at idle spikes back up to where it should be, or at least climbs, with the vacuum line disconnected then the regulator is likely at fault. If it stays the same I'd look at the fuel pump first.

At least if it's the pump you are looking at the external high pressure pump and not the one in the tank.
Brand new fuel pump. Pulling the vacuum line off at idle it shoots the fuel pressure up to about 43-45psi.
 

adsm08

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wildbill23c

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Ok, regulator is bad.
Thought so, and driving it without the regulator vacuum line connected is a bad idea correct? At least it would be my assumption without proper fuel regulation it could cause problems. Diaphragm could fail and spray fuel all over I'd think.
 

adsm08

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Thought so, and driving it without the regulator vacuum line connected is a bad idea correct? At least it would be my assumption without proper fuel regulation it could cause problems. Diaphragm could fail and spray fuel all over I'd think.
If it was your only option for transportation you could probably get away with it, but I'd cap the port.

Since I know you have other vehicles, I'd avoid driving it until it's fixed.
 

wildbill23c

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If it was your only option for transportation you could probably get away with it, but I'd cap the port.

Since I know you have other vehicles, I'd avoid driving it until it's fixed.
Exactly what I thought LOL, I got the Bronco 2 and the Jeep...the pickup is going to be my weekend DIY project vehicle so its not like its my only way around anyhow.
 

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I never understood the EGR delete either unless you can control your computer which most of us can't. However I have seen (in dually diesels setup for towing heavy RV's) where doing an EGR delete was beneficial. The guy had a bulldog computer/programmer in the dash and had a lot of engine work done and he swears by it. Says it tows way better and gets better fuel mileage but then again he has a programmer in the dash so he could change stuff on the fly. I personally wouldn't do an EGR delete.... It's there for a reason so just fix the damn thing, it's not that hard or expensive.
 


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