1995 Ford Escort, sputtering/bucking at highway speeds (EGR related?)

The car: 1995 Ford Escort LX station wagon. 1.9L four cylinder engine, automagic transmission.
The problem: The engine runs well most of the time, starts well, idles well. The
problem is that on the highway, at 45mph+ speeds, the car bucks and sputters sometimes. The problem seems to be EGR related. It occurs when the EGR valve opens (or should open).
Things I've tried: I disconnected and plugged the vacuum line on the EGR valve, and the bucking and sputtering doesn't occur. I get smooth running, but I also get more pinging under moderate loads, and I get a check engine light because the computer can tell the EGR valve isn't really opening when the solenoid provides vacuum to it. The codes indicate an EGR problem (obviously because I disonnected the EGR valve and plugged the vaccum line).
I picked up a good condition used EGR valve from a parts yard, and I thoroughly cleaned the carbon gunk out of that valve, getting it looking very clean and almost new. I tested this valve and it works and seals properly when closed, flows well when open. I installed it and it didn't fix the problem. The old valve looked very similar with some carbon buildup in it, but it functions properly. The EGR pipe that the valve attaches to also had scaley carbon stuff in it, but with the EGR valve disconnected from the pipe and the engine running, there was exhaust coming out of the pipe.
I really don't want to just "throw parts" at it. The budget is tight right now. What can I check next?
-- Racer X
1984 VW Jetta Diesel GT 1992 Mazda Miata 1994 Caravan (OK, maybe it's a keeper, but I still want a VW Caddy) 1995 Ford Escort (Hey, it was free) 1983 VW Rabbit GTI (ITB racer) 1988 Mazda RX-7 (Soon to be ITS racer) 1992 GMC Topkick (portable garage for racecar[s])
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racer snipped-for-privacy@winning.com (Racer X) wrote in message

Nobody has any suggestions?
According to the factory service manual, "The amount of recirculated exhaust gas depends upon: * Engine RPM * Intake Vacuum * Exhaust back pressure * Engine coolant temperature * Throttle position"
I'm assuming that all of those except for maybe exhaust back pressure and possibly intake vacuum are monitored by the ECU (and sensors connected to the ECU). I'm also guessing that I'm probably getting too much exhaust gas in the intake, so I might have too much exhaust back pressure. It seems peppy enough, but how would I check for blockage?
There is some sort of electrical gizmo on the firewall right next to the vacuum valve/solenoid that controls the vacuum line to the EGR valve. That piece has a rubber hose going to the EGR pipe right near the EGR valve. Is that a sesnor for exhaust back pressure? Could it be bad? Could that be the cause of my problem?
-- Racer X
1984 VW Jetta Diesel GT 1992 Mazda Miata 1994 Caravan (OK, maybe it's a keeper, but I still want a VW Caddy) 1995 Ford Escort (Hey, it was free) 1983 VW Rabbit GTI (ITB racer) 1988 Mazda RX-7 (Soon to be ITS racer) 1992 GMC Topkick (portable garage for racecar[s])
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I think your barking up the wrong tree. check plugs, wires, fuel pump first if its been a while. disconnecting the egr is probably just masking the real problem.
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wrote in message

I had a similar problem (Thread is 'Vacuum Monster Strikes'). They have a device they can hook up and check the back pressure for you. The fellow I took the truck to told me this. He just revved the engine once, told me the Cat was plugged. Twenty minutes later I had what felt like an additional 100 horsepower.
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Plugs, wires, fuel filter and air filter are all new (changedless than 5,000 miles ago). Bad plugs or bad wires would make it misfire almost all the time, too.
The reason I think it's EGR related is because it only misfires when the EGR valve opens. I hooked my vacuum guage up on a long hose with a T connector (so I can hold the vacuum guage and ride in the passenger seat), and it runs perfect except when the vacuum comes on in the line to the EGR valve. With the EGR valve open, it misfires, sputters and bucks. If you stand on the gas pedal, the EGR valve closes and it immediately clears up. If you slow down and the engine speed drops below 2000 RPM's, the EGR valve closes (no vacuum on the line), and the thing clears up immediately. The only time it misfires or sputters is when the EGR valve is open. It always misfires and sputters when the EGR valve is open, and never misfires or sputters when the EGR valve is closed.
I also don't think I have blockage in the exhaust. I get about 21 inches of vacuum with the thing idling, and about 23 inches of vacuum with the thing in neutral and running at 3000-3500 RPM's. Usually with a blocked cat or blocked exhaust, you see a drop in vacuum with no load at higher RPM's. Also, the engine pulls good. It doesn't have problems going up hills or lack for power (at least no more than you would expect for a little 4 cylinder in a fairly heavy station wagon).
I haven't checked backpressure, but I will hook up my pressure guage tonight to the EGR pipe and see what kind of presure is in the exhaust manifold and EGR pipes. What's a reasonable reading for that? How much pressure is normal and what level indicates blockage?
-- Racer X
1984 VW Jetta Diesel GT 1992 Mazda Miata 1994 Caravan (OK, maybe it's a keeper, but I still want a VW Caddy) 1995 Ford Escort (Hey, it was free) 1983 VW Rabbit GTI (ITB racer) 1988 Mazda RX-7 (Soon to be ITS racer) 1992 GMC Topkick (portable garage for racecar[s])
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racer snipped-for-privacy@winning.com (Racer X) wrote in message

Not sure if this will help, but it may promote more ideas. The EGR valve is meant to pass exhaust gasses back into the inlet manifold at appropriate times, to reduce combustion temperatures. It does this to reduce the amount of Nitrous Oxide? being created, some nasty exhaust emission. Could loose carbon build-up be coming in via the EGR valve and temporarily fouling the spark plugs? Could the combustion temperate become too low for the heat range of the spark plugs you are using? Does the vacuum switch hold the EGR open steadily, or is it opening and closing it when it should just hold it open?
David Jory
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On 18 Aug 2004 19:21:03 -0700, snipped-for-privacy@hotmail.com (David Jory) wrote:

Oxides of Nitrogen / NOx

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Scott M opined in

I was gonna disagree with Racer, but then started to think about it..\\
It DOES seem an unusual problem.
So first, get a replacement "gizmo"... thats called a DPFE sensor.. from a salvage yard. Then check fuel pressure. Could be the Fuel Pressure Regulator too...
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OK, "new" used "gizmo" is in. That's the "Exhaust Gas Recirculation pressure valve sensor" according to my shop manual. This did not fix the problem.
I also checked the pressure at the EGR pipe fitting on the exhaust manifold. The needle on my guage bounced back and forth from the exhaust pulses, so the exact reading was tough, but it seemed to be bouncing really close to zero. Even at 3000-4000 RPM's (no load), it stayed at near zero. I couldn't really test under load, so I don't know for sure, but it sure doesn't seem like the cat or exhaust is blocked.
I guess the fuel pressure regulator is the next thing to check. I'll hook up my guage and see what the fuel pressure does when the EGR valve opens. That regulator does seem to have a vacuum fitting on it to sense intake vacuum, so maybe it's faulty or getting confused.
Thanks again to all who have replied.
-- Racer X
1984 VW Jetta Diesel GT 1992 Mazda Miata 1994 Caravan (OK, maybe it's a keeper, but I still want a VW Caddy) 1995 Ford Escort (Hey, it was free) 1983 VW Rabbit GTI (ITB racer) 1988 Mazda RX-7 (Soon to be ITS racer) 1992 GMC Topkick (portable garage for racecar[s])
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I had a very similar experience. Turned out to be a bad coil.
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James Caldwell

e-Mail: snipped-for-privacy@RacingDrives.com
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