95 Escort: how to test EGR & PFE ?

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I have a 1995 Ford Escort LX wagon, 1.9L engine automatic trans.
I'm making some tests of the EGR subsystem using the Chiltons manual et al., but I'm not sure I'm doing some of it correctly.

I"ve made some static tests of the valve itself, and it passes that.
But one dynamic test suggests bringing the engine rpm to 2000-2500rpm, and checking to see that the vacuum to the EGR rises to 4-6" Hg. Mine goes up to about 6-8" momentarily and then drops right back down to almost nothing.
Does anyone know. . . should it stay up there while the rpm is at 2500, or should it be momentary?

PFE / DPFE (Pressure Feedback Electronic)
The Chilton test of the PFE does not seem like a valid test. It requires you to remove the sensor connection and probe the voltage at PFE terminal - but then how would you get any voltage reading without any power source? I'm getting nothing, and it's a $165 part. Or it's a good test and the PFE failed totally (there are no codes set). Any other way to test this?

After I have test results I might post a question about my overall stuttering problem, that is, with the car.

posted by  Kbarb

My 95 wagon is also stuttering at different times. Have you replaced the fuel filter ? I have the manual trans. I am changing the filter tomorrow and will let you know if that solves the problem.....

posted by  ninertango

Yes I have replaced the fuel filter to no avail. And I have good fuel pump pressure.

I've bought a Ford shop manual on Ebay and I'm waiting for it to arrive so I can be sure I've got the correct test procedures to work with.

But I'm almost certain it's the EVR (EGR vacuum control solenoid).
My reasoning is this:
The problem only happens when the system is warm and under partial acceleration. When it's cold, or under full acceleration (floored) it doesn't happen. Warm and partial acceleration are exactly the conditions under which the EGR system functions, and cold and full acceleration are when it doesn't - the computer prevents it, as far as I know, (but I'm not the definitive expert.) Also, the fact that it doesn't hesitate when it's cold and under full acceleration tells me that it's not the injectors, nor the ignition system - there's no reason why they wouldn't cause the problem under these conditions. It's probably the EGR subsystem, although there are a few other things that can cause hesitation.

Also, that EVR solenoid controls the EGR valve by opening and closing very rapidly (dithers it) - the more time it's open the more time the vacuum to the EGR is on, and the more of that time it's closed, the more time the EGR is closed. It seems to me a part like that would wear out over time, and indeed mine did not hold vacuum as it should. It turns out the Ford parts dealer stocks this part because they sell it a lot - not because it's a bad design, but because they inherently wear with the dithering.

My EGR valve itself passes the static vacuum tests so it's not the EGR valve itself.

But I need that manual to check the PFE, so I'm waiting.

I'll post when I get more results.

ps: what's that ninertango all about? I just went to a tango party last night.

posted by  Kbarb

Problem solved - it wasn't EGR or PFE.

It turned out that the problem was that I had gapped the plugs about 4 or 5 thousandths too small. I also changed the spark plug wires but I'm pretty sure it was the small gap that caused the problem. Why that causes a hesitation, and only when warm, and not at full throttle, is a mystery to me. Perhaps the spark was not of sufficient high voltage with the small gap. But the solution was cheap enough.

One thing I discovered in the process was that those little circular-disk plug gapping tools are not very accurate. I checked it with a micrometer, and it was about .005 larger than stipulated.


posted by  Kbarb

if it stutters after going down the highway for a few minutes and you have to floor it to "clean it out", you might want to clean your maf sensor. tempos and escorts tend to do that...

posted by  dodger65

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