EGR issue, 98' XLT

[jmvb]

Hi

If you take a look to my post, you can read all my XLT nightmares..

http://www.explorerforum.com/forums/showthread.php?t=434335



Well, I'm still in the game, now, I'm trying to figure out, how the EGR works

After my burning episode, the EGR valve is always open, I mean, the vacuum hose is always in suction, so, in idle, the engine run rough.

If I unplug the EGR hose, the idle is smooth.

Any tip?

 

[shucker1]

EGR means Exhaust Gas Re circulation.

The system takes exhaust gas and puts it back into the intake of the engine to cool the combustion temperatures down and reduce NOx (Oxides of nitrogen) emissions.

Nasty stuff that pollutes the air.

You may have a bad control solenoid. Follow the the tube from the EGR valve to the next valve and unplug the electrical connector..

If there is no change the control valves is bad. If there is a change something in the computer is tell the system to stay on?

 

[jmvb]

EGR means Exhaust Gas Re circulation.

The system takes exhaust gas and puts it back into the intake of the engine to cool the combustion temperatures down and reduce NOx (Oxides of nitrogen) emissions.

Nasty stuff that pollutes the air.

You may have a bad control solenoid. Follow the the tube from the EGR valve to the next valve and unplug the electrical connector..

If there is no change the control valves is bad. If there is a change something in the computer is tell the system to stay on?

You mean the DPFE sensor?

Already I'd unplugged it, and nothing happens, rough idle, EGR open.

No computer changes at all, only the fire episode, in that area... (no DPFE sensor cables melted)


EDIT: found the problem:
The green hose, which go to EGR, was swapped by the white one, my mistake...

BTW, where the white hose go? had something to do with the A/C? (because it is working again )

 

[manimal]

the white line is part of the HVAC system

Not sure if exactly the same on your year, but here's an idea

http://www.explorerforum.com/forums/showpost.php?p=1541279&postcount=18

 

[shucker1]

You mean the DPFE sensor?

Already I'd unplugged it, and nothing happens, rough idle, EGR open.

No computer changes at all, only the fire episode, in that area... (no DPFE sensor cables melted)


EDIT: found the problem:
The green hose, which go to EGR, was swapped by the white one, my mistake...

BTW, where the white hose go? had something to do with the A/C? (because it is working again )

No, the DPFE sensor reports to the computer how much EGR flow is going into the engine.

That needs to be plugged in. If not the computer will see a zero value and try to open the valve more to get what it needs.

Tomorrow I take a picture of my emissions decal and post so you can see where all of the emissions tubing should go.

Perhaps you already have that decal under the hood?

 

[Flash]

No, the DPFE sensor reports to the computer how much EGR flow is going into the engine.

That needs to be plugged in. If not the computer will see a zero value and try to open the valve more to get what it needs.

What's the nett result of that?
How does it affect the way the engine runs?

 

[shucker1]

Without getting down into the actual block logic.

DPFE means differential pressure flow exhaust.

2 lines attached, one line is (Hi Pressure Side) and the other is (Low pressure Side)

There is a small orifice between the two connections. There are other ways to get the same result but these are slightly more complex.

When you have a flow across any kind of orifice there with a difference in pressure on either side. The sensor see this pressure difference and turns it into an electrical signal the computer can understand. Usually 1 to 5 VOLTS DC.

The computer knows, because of the internal written logic, "If I am running in this condition because of what all of my other sensors are telling me I need to see this much value out of the DPFE sensor. If I don't, I can open the EGR valve to get what I want. If I see too much value I can close the EGR valve".

If you unplug the sensor it will see a zero and say to itself "Open More, I need this" plus it should also throw a code as a faulted sensor. (Less Than 1 volt with some tolerance factor involved)

I well written operating code should also fault out (Throw a Code) "Over Value" more than 5 Volts.

A full open EGR will continue to flood the engine with Exhaust gas and kill combustion making tit run like crap and low load levels.

Plus with a major trouble code like bad DPFE sensor the computer goes "Open Loop" and runs by a pre-programmed set of values just to try and stay running. This will kill your gas mileage because the computer is not trying to get the best efficiency it can with the best emissions.