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Topic: EGR System and EGR Tube Operation Questions (Read 896 times) previous topic - next topic

EGR System and EGR Tube Operation Questions

Is there an operation explanation of this anywhere? I don't see one in my shop manuals. I'm looking to find out if the EGR system is even functional in Park/Neutral, is the exhaust gasses even recirculate under these conditions. Or if they are supposed to, and they are not, what would cause this. I got the check engine codes, we all discussed in other threads, but I'm trying to look outside the box on this one.

Some of you may know, or could just point me in the direction of the information. I tried an advanced search, but didn't come up with what I was looking for.

EGR System and EGR Tube Operation Questions

Reply #1 –
I don't know every thing about this but i asked my uncle about this a month ago.  He told me that if the if EGR is on during idle, stumble and even stalling will likely result.  A bad O2 censer could be why it is doing it during idle but not 100% sure of that.  Sorry i can't help more!

EGR System and EGR Tube Operation Questions

Reply #2 –
I dont have the 5.0 memorized like i do the 3.8CFI. 
It stands to reason they work prety much the same way.

At idle in park or N, and with a warm motor, i dont think you have active "exhaust gas recirculation".
Thunderchicken has this stuff memorized and he posted up a diagram of the path this system takes which explains a lot that words have difficulty doing.  The diagram is in the shop manual(s) if you have the emissions one but not in the EVTM.

what I think i know...
-the egr has a vac line from an electrical solenoid
-the solenoid is a cut off valve / check valve that allows flow or prevents it.
-the solenoid will get power to move the plunger and allow vac pressure / suction at the EGR.
-the solenoid will get power at an rpm value that I do not know however i do know that with a warm motor, there is no vac pressure on the egr vac line.  There will be a slight pressure on the vac line when you first start up because this is the eec doing its diagnostic and recording codes. On a cold motor,the engine will rev a little high just so it can produce the vac and electrical signals.
-When you are in Park or Neutral, the egr solenoid should not be active so no flow of vac pressure to the egr.
-When the egr does get vac signal by way of an energized EGR solenoid, there is a rubber diaphram in the EGR that is moved upward.  the opposition to the diaphram is a simple coil spring that returns the diaphram to its static state when no vac  signal is present.
-The diaphram simply pushes on a metal shaft that is a part of the EVP sensor mounted atop the egr.
-on the mounted end of the EGR at the intake, the diapram is fabricated with a hunk of metal that opens up a port to allow exhust gas to travel back through the throttle body area and reburn in the cylinders.  This is the part you can push in on by hand, its the check valve so to speak that cuts off or allows the exhaust to loop back into the intake.
**the part I never really understood is that it appears we have emissions managment on the passanger bank only as there is no smog pump tube on the driver side header.  I am probably wrong but its just an observation.
-The evp sensor is nothing more than a variable resistor that sends resisitivity / voltage signals to the computer.  From here, i have no idea what the eec does with the info other than richen or lean out based on other inputs from the TPS/O2/ISC/ECT/ ect ect but the Map sensor is the biggest player as it is a parallel device off the evp "reference".

=so, once an rpm is reached (a value i dont know) then the egr solenoid is picked to energize and allow the vac pressure path to be found on the egr suction port / fitting.  The internal diaphram moves up by way of suction and pushes on the EVP sensor shaft.  while the EVP sensor voltage changes in reference to the MAP sensor , the diaphram is in full control of a plunger at the intake side by way of the plunger that allows exhaust gas to recycle through the intake for reburn.


Here is a test you can do on the EVP sensor (in the diy link in my sig)
EVP test (egr sensor)
wire id...
EEC PIN 26 "VREF" orange/white (parallels off to map)
EEC PIN 27 "EVP SIGNAL" brown/light green
EEC PIN 46 "SIG Return" black/white (parallels off to self test conn)

disconnect vac line
disconnect elec conn
hook ohm meter up to the VREF adn EVP Sig contacts
hook up vac guage or apply vac to egr
ohm meter should start out at about 5.5k ohms.
as vac is increased to max, resistance should bottom out to no less than 100ohms.
*you can add vac pressure as desired to see the resistivity change and check for intermittant opens in the windings of the EVP variable resisitor.

key on, engine off
cap off vac fitting on evp sensor
measure for 4 to 6 volts dc between VREF and SIGNAL RETURN (ground)
 

EGR System and EGR Tube Operation Questions

Reply #3 –
Thank you JCassity.

I really need one of those ed emissions books, they are just hard to find, and when you can find them, people want their weight in gold. :/