CA Smog Help - EGR

Man, I haven't smogged the mustang in about 4 years cuz its been down. So they have this new smog rule where you have to print out the EO PDF files (from CA's website) for every aftermarket product on your car that could effect emmissions. It was a bunch of fun trying to get around adding a MAF sensor to an 87, luckily one of the PDF files didn't have a year range on it.

After an hour of printing I took it down to the test only center and surprisingly passed everything except the EGR valve test. I am pretty unfamiliar with how this system works. The guy said it is holding vacuum well, so the valve is likely good, and I know I replaced it back in the day. But it didn't "stop the motor from running" when he ran a test on it.

Comparing my current vacuum setup to the TMOSS diagrams, everything looks like it should be set up properly. The holes in the valve and the EGR Spacer thing connected to the Throttle Body look clean. Any info would be good info so I can try to get this thing to pass smog soon. Until then it will be driving around with 08' stickers and an un-dated one-day moving permit ;)
 
  • Sponsors (?)


Some basic theory to clarify how things work is in order…

EGR System theory and testing

The EGR shuts off at Wide Open Throttle (WOT), so it has minimal effect on performance. The addition of exhaust gas drops combustion temperature, increases gas mileage and reduces the tendency of the engine to ping. It can also reduce HC emissions by reducing fuel consumption. The primary result of EGR usage is a reduction in NOx emissions.

The EGR system has a vacuum source (line from the intake manifold) that goes to the EVR, computer operated electronic vacuum regulator. The EVR is located on the back of the passenger side shock strut tower. The computer uses RPM, Load. and some other factors to tell the EVR to pass vacuum to open the EGR valve. The EGR valve and the passages in the heads and intake manifold route exhaust gas to the EGR spacer (throttle body spacer). The EGR sensor tells the computer how far the EGR valve is open. Then computer adjusts the signal sent to the EVR to hold, increase or decrease the vacuum. The computer adds spark advance to compensate for the recirculated gases and the slower rate they burn at.


attachment.php


Troubleshooting:
There should be no vacuum at the EGR valve when at idle. If there is, the EVR (electronic vacuum regulator) mounted on the backside of the passenger side wheelwell is suspect. Check the vacuum line plumbing to make sure the previous owner didn’t cross the vacuum lines.

Diagram courtesy of Tmoss & Stang&2birds. (the diagram says 88 GT, but the EGR part is the same for 86-93 Mustangs)
88Stang5.0Vacuum.gif


The EGR sensor is basically a variable resistor, like the volume control on a radio. One end is 5 volt VREF power from the computer (red/orange wire). One end is computer signal ground (black/white), and the middle wire (brown/lt green) is the signal output from the EGR sensor. It is designed to always have some small voltage output from it anytime the ignition switch is the Run position. That way the computer knows the sensor & the wiring is OK. No voltage on computer pin 27 (brown/lt green wire) and the computer thinks the sensor is bad or the wire is broken and sets code 31. The voltage output can range from approximately .6-.85 volt.

The EVR regulates vacuum to the EGR valve to maintain the correct amount of vacuum. The solenoid coil should measure 20-70 Ohms resistance. The regulator has a vacuum feed on the bottom which draws from the intake manifold. The other vacuum line is regulated vacuum going to the EGR valve. One side of the EVR electrical circuit is +12 volts anytime the ignition switch is in the run position. The other side of the electrical circuit is the ground path and is controlled by the computer. The computer switches the ground on and off to control the regulator solenoid.



EGR test procedure courtesy of cjones

EGR test procedure courtesy of cjones

to check the EGR valve:
bring the engine to normal temp.

connect a vacuum pump to the EGR Valve or see the EGR test jig drawing below. Connnect the test jig or to directly to manifold vacuum.

Do not connect the EGR test jig to the EVR (Electronic Vacuum Regulator).


apply 5in vacuum to the valve. Using the test jig, use your finger to vary the vacuum

if engine stumbled or died then EGR Valve and passage(there is a passageway through the heads and intake) are good.

if engine did NOT stumble or die then either the EGR Valve is bad and/or the passage is blocked.

if engine stumbled, connect EGR test jig to the hose coming off of the EGR Valve.
Use your finger to cap the open port on the vacuum tee.
snap throttle to 2500 RPM (remember snap the throttle don't hold it there).
did the vacuum gauge show about 2-5 in vacuum?
if not the EVR has failed

EGR test jig
attachment.php


To test the computer and wiring to the computer, you can use a test light across the EVR wiring connectors and dump the codes. When you dump the codes, the computer does a self test that toggles every relay/actuator/solenoid on and off. When this happens, the test light will flicker. If the test light remains on the computer or the wiring is suspect.

To check the EVR to computer wiring, disconnect the EVR connector and connect one end of the Ohmmeter to the dark green wire EVR wiring. Remove the passenger side kick panel and use a 10 MM socket to remove the computer connector from the computer. Set the Ohmmeter to high range and connect the other ohmmeter lead to ground. You should see an infinite open circuit indication or a reading greater than 1 Meg Ohm. If you see less than 200 Ohms, the dark green wire has shorted to ground somewhere.

Late Model Restoration may still have the Ford Racing M-12071-N302 kit with the EGR valve & sensor along with the ACT & ECT sensors for $45. See http://www.latemodelrestoration.com/iwwida.pvx?;item?item_no=M12071N302 1&comp=LRS for more details
 
Well, thanks to jrichker you now know EVERYTHING there is to know about the EGR valve on your car!

Let me simplify: Okay, so the smog nazi put vacuum on the EGR and it didn't stall the engine: This means not enough is flowing, which simply means it is probably clogged or partly clogged. This can be a mofo on a 5.0HO because the way the gasses flow.

Remove the EGR valve and see the passages both in the EGR valve and the manifold/tb spacer. Tape up the manifold with a piece of duct tape, one piece on each hole. Start the car. Remove the intake side and see if you are getting vacuum, it should suck pretty hard, probably stall the engine. If so, your good there. Remove the exhaust side and you should have a decent amount of exhaust gas coming through. If you do, your good there, if not, you have clogged exhaust ports.

Cleaning the intake side, the worse case you will have to remove the spacer and scrub it out. The exhaust side, not that one could suck, because if you are not lucky enough that the clogging is just in the EGR spacer, you're going to most likely have to pull the manifold off and clean it out with a bore brush and lots of carb cleaner. The EGR gets its gasses all the way from the head. I doubt it's clogged there, and you can from there probably clear it out with chemicals. Use compressed air to see if you have flow. If you do, you should be good.
 
I live in cali and you don't have to print out ****, nor go to a referree.....if a smog tech tells you that crap, move on to the next one.

I agree, the passages are probably clogged. The port in the head and bottom of the intake is pretty large, so like mentioned, start at the top where the egr mounts...the problem is prob around that area.
 
Alright guys just need a little interpretation of the testing. The car pulls 18 (whatever the units are for vacuum) at regular operation. So first put the vacuum gauge to the vacuum line going into the EVR and measured 12. then let the car get up to operating temp and connected the vacuum gauge to the line between the EVR and EGR valve. Snapped the throttle a few times and zero reading on the gauge. So I will be replacing the EVR.

Next went to test the EGR Valve. Connected the 12 vacuum from the line going into the EVR directly into the EGR valve (bypassing the EVR completely). Could visually see the EGR diaphragm moving, but engine idling did not change. So then went with the taping method of testing. Word of caution for this method, hang on tight to your duct tape because the intake side sucks like a mother. So after sucking the tape clear through the first time, that means the intake side is not clogged. Also connected the 12 vacuum line from manifold directly to EGR valve while not connected to EGR spacer and the valve definitely opens up all the way.

So if the EGR valve is opening properly when vacuum is applied and the intake side is sucking, does that mean for sure that there is not enough exhaust gas being fed to the EGR valve? the bottom end of the motor is brand new so highly doubtful of any clogs from the heads down. At this point should I take the upper intake manifold off and clean the hell out of it to see if it is clogged somewhere? I'm stumped because the upper intake (trick flow) has less than 20k miles on it, didn't think it could be clogged so easily.
 
Which trick flow intake do you have? Does it have the provision for the egr? In other words is the internal plumbing even provided for the egr? Some of them don't have it
 
Some of the intake gaskets block off the EGR passages, others have two extra pieces that can be used for the same thing. It is possible that this may be the source of your problem if the manifold has the EGR passages in it.
 
Ohh good ideas! Checked with Trick Flow and the intake manifold definitely has the provision for the EGR and is CA smog legal; came with stickers and EO numbers. Also confirmed gasket part numbers with them to make sure the correct ones were used, they checked out also.

Is it possible that EGR valve is opening but not properly? Or if no exhaust gas is coming through the opening at operating temp, anything else I can check? Really wish this thing could pass smog soon.
 
Yeah with it removed and vacuum applied do you see the pintle moving? Mine held vacuum, and collapsed the diaphragm but it did not move the pintle. I actually soaked it in cleaner, and tapped it with a hammer then it worked like new again not getting stuck.
 
The guy who helped me diag the problem said that he thinks replacing the precats will solve the problem, the guy at the muufler shop who quoted $230 per cat plus $30 to install said replacing the backs will solve the problem

Here is what I am looking

http://www.oreillyauto.com/site/c/d...=Search_02404_1134065_3065&pt=02404&ppt=C0022

how about this, does any one make a system that is California legal from the shorty pipe back?
 
Yeah with it removed and vacuum applied do you see the pintle moving? Mine held vacuum, and collapsed the diaphragm but it did not move the pintle. I actually soaked it in cleaner, and tapped it with a hammer then it worked like new again not getting stuck.

I'll have to ad the hammer trick to my EGR writeup...:D