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pinpoint tests of egr system; bad info in autozone guide?

ikeru

New CEG'er
Joined
Nov 2, 2006
Messages
17
having just done a good bit of work on my '97 tour, i figured i'd do something about the inspection that's going on close to 2 years expired. cel p0401. pretty common to all fords from what i'm seeing. i read through the forums and archives on this site, checked the pinpoint tests on the ford cd, but mostly followed the info from autozone's repair guide: http://www.autozone.com/shopping/repairGuide.htm?pageId=0900c152800a8aa6

egr valve tested a la 'suck test'. it's fine. valve opens and closes and the car stumbles when vacuum's applied at idle.

now onto the evr solenoid and dpfe sensor. and this is where i get thrown off.

to start with, definite typo in the az guide:
Apply battery voltage (approximately 12 volts) and a ground to the EVR solenoid electrical terminals. Attempt to lightly blow air, once again, through the solenoid.
  1. If air does not pass through the solenoid, replace the solenoid with a new one.
  2. If air does not flow through the solenoid, the solenoid is OK.
i'm guessing that 'b' should read 'if air does flow through.

so then, i have two evr solenoids in hand, one old and one new. they both seem to behave the same. very little air can pass through regardless of whether they're getting no power or 12 volts and a ground. to begin with, no air should pass through when not powered, so that's one problem. and the solenoid should energize and open up if fed 12v and a ground, right? both the old and new one are no good maybe?

now the dpfe. the ford cd and az guide's diagram shows the dpfe's sig rtn connection to be the middle pin. when i backprobe that connector, i get nothing: 0v with or without vacuum. checking out the other two pins, i see that the bottom one is at a constant 5v while the top one is at ~0.95v. now with the top pin backprobed and vacuum applied, the top pin's voltage goes up to 5v as it should. so, is the autozone guide off or is there something funky with my wiring?
 
First thing is that the EVR is powered by pulsewidth modulation. It is never on more than a 50% duty cycle and may be damaged by prolonged battery voltage. The orifice in the EVR is quite small and blowing through it would give questionable results. This test idea would work better if vacuum was applied to the input to check for off leakage, and a short touch of power will relieve the vacuum. By connecting a vacuum gage in place of the EGR valve you can also test for idle leakage and a quick rev should give 5 in. hg. output.

A better way to judge The EGR valve flow would be to put your vacuum gage on the downstream DPFE hose and manually opening the EGR valve while keeping the RPM's at 1500 or so. You should see about 10 in. hg. If you see much less the EGR valve or intake passage is restricted. If you see much more the EGR tube orifice is clogged.

I don't remember the DPFE wiring, but this may help in your testing.
http://www.contour.org/ceg-vb/attachment.php?attachmentid=1555&d=1185934393
 
I'd say you have found a typo and are correct in your assessment.

When full voltage is applied to the EVR solenoid, it should open and pass full vacuum. You are likely correct in that both are defective.

As for the DPFE output readings, the output should be between .24 and .67 volts with the system at rest. You have the correct wiring pin-out info.

One thing to keep in mind, a restriction in the EGR ports behind the throttle body can cause insufficient flow while still allowing the "suck test" to show an operable condition.

Steve


PS

Roger:

The PCED (Procedure HJ34) does call for grounding the EVR solenoid low side while monitoring vacuum at the EGR valve hose with a gauge and looking for full manifold vacuum when the valve is opened. I wouldn't suggest leaving the solenoid continuously connected for a long period of time, but I doubt it would adversely affect it.
 
ahh - thought that evr solenoid was a straight 12v. good to know - i only grounded out the connection for a few seconds at a time to see if i could hear it power on and to vacuum test the ports. but now i'm wondering if there's another angle to my problem. i called up the dealership today to get a quote on a new solenoid and the parts guy asks me for the calibration #? i told him that i clearly knew of no such thing. then he says that there are ford/motorcraft dpfes and evr solenoids manufactured with two different calibration settings. the dpfe that's in there looks like a cheap aftermarket replacement (airtex or standard motor maybe?) and the new evr solenoid i bought was a cheap $25 duralast replacement from autozone.
 
There have been changes in these sensors construction and appearance, but not in function. The system is closed loop and can handle a certain amount of variation anyway.

If the EGR passages in your intake have not been cleaned out yet, I suggest that you do that first. Due to the design there is zero chance that they are still fully open. You absolutely must run a coathanger or the like from the intake over to the EGR mount till the passage is clear, clean out the slots in the TB mounting flange, and ensure that there are no holes in the EGR tube. Make sure the EGR valve fully opens and is not clogged while you have it off.

As the miles rack up and blowby increases, this becomes a yearly task.

If you still get the code after the cleaning to ensure sufficient flow, the DPFE or it's hoses to the EGR tube are suspect. The EVR usually causes excessive flow at idle or a total noop.
 
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