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Old 08-18-2009, 05:00 PM   #1
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EGR valve issues?

Serious answers only please. I have a 1995 Ford F-250 XL 5.8L 351 c.i. engine. My check engine light comes on periodically when I drive. When I bought the truck a year ago the gas mileage wasn't too bad, about 9-10 mpg. I've only put about 3,000 miles on it this past year, and now the needle drops just driving it across town. I work at a Chevy dealership, and I've worked at another Chevy dealer as well as a Ford. I've always done my own work on my cars and am currently restoring a 1967 Mustang, so I have decent knowledge under the hood. I scanned the truck and it has a stored code for EGR valve voltage too high (stuck open). How bad could this be hurting my gas mileage? It's $160 for the valve and sensor even after my discount, and being a college student that's a lotta $ to pay. I'm selling the truck and need it running perfect when I do. Please, serious answers only, and help is greatly appreciated!
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Old 08-18-2009, 05:17 PM   #2
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EGR valve issues?

EGR valve stuck open will cause a serious dent in your mileage and performance. At $160 bucks you will be saving yourself alot of money by replacing it.
I would go to a local junk yard and find one on a wreck. though you dont know what you are getting going that route you could save alot of money getting another egr valve that way and solve your problem to boot. you just ned it to work long enough to sell it so maybe that would suffice.
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Old 08-18-2009, 05:40 PM   #3
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EGR valve issues?

Vile fly is correct.. the plate the sensor rests on has a habit of moving and causing the light to come on, or like some of the EEC IV trucks I've seen... It sets the code but doesn't affect driveability at all (Or fuel economy unless the sensor is screwed up real bad. Try changing the sensor with one from say Autozone or Napa and see if that fixes some of it (after you measure the voltage)..

Fords have a bad habit of the EGR sensors going bad.. the actual EGR has no real issues (except on the older vehicles like yours with the plate or the diaphram finally blowing up).. but the sensor reports bad info to the PCM and it tries to correct wrong.

The egr actually functions properly usually but because of the plate, it causes the light issue... As Vile fly stated..check it.... it shouldn't be open at all (usually bad idle is one sign EGR is open) at sensor voltage should read .5v or so at sensor wire.

One of the issues these trucks did have was fuel pressure regulators going bad on the rail and dumping fuel in to the engine.... usually more than 45psi of fuel pressure shows that the regulator is bad and will cause what you describe IMO (normal is 30 running 40 psi on goose)

Pull the plugs and check them, the mechanics at the Chevy dealer after ribbing you will read the plugs for you and give ideas.

Another thing is check the fuel filter for clogs... It's a bear to get to and most take it to speedy lubes just because of where it is..... Fuel filter clogs up and the engines seem to run richer due to it.

Other than that, it would take me looking at it for ideas...
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Old 08-18-2009, 06:12 PM   #4
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EGR valve issues?

EGR valve should be opening at higher RPM's and closing at lower ones. Check the shaft positioin on the EGR valve with the engine idling (you might need a flashlight and mirror on an extension rod to see it on your vehicle). When the engine is revved up, the shaft should move away from the engine. If its not moving or it moves open but doesn't close all the way, it could be that the valve seat of the valve is broken and holding the valve open. If you do end up replacing it, clean out the carbon if there is any in the opening of the engine that leads to the EGR valve.
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Old 08-18-2009, 06:38 PM   #5
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EGR valve issues?

Open the hood, find the valve and check its operation. With the engine running, watch the diaphragm and then operate the throttle. When you gun the engine, you should see the diaphragm move. If it doesn't, there may be a dried-out and damaged rubber vacuum hose (quite likely) or else the valve is clogged up with carbon. Pull the valve out and shoot it full of carburetor cleaner to dissolve out the carbon. You should be able to move the operating diaphragm by sucking on the vacuum tube. While you're in there, start the engine without the EGR valve in place and shoot carburetor cleaner into the holes that lead into the intake manifold: one should have vacuum, and the other should have exhaust pressure.
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Old 08-18-2009, 07:18 PM   #6
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EGR valve issues?

Get out your jumper leads and backprobe the egr solinoid.
ok. 1st thing......attempt to kill the motor at idle using the egr
solinoid. apply ground to the proper wire(not red) and see if the egr valve operates, killing the motor @ idle.
if it does operate, but doesn't kill the motor......you have some cleaning to do.
if it operates, and kills the motor.......the valve and solinoid are ok. (the solinoid should also vent the egr valve vacuum when de-energized)
Now.....for the tricky part. AFTERMARKET EVP SENSORS SELDOM READ CORRECTLY.
1. Turn the key on and check the voltages at the Exhaust Gas Recirculation (EGR) Valve Position (EVP) Sensor. The Brown/White (BN/W) should be 5v, the Grey/Red (GY/R) is ground and must read 0.1v or less at all times. The Brown/Green (BN/GN) is the signal and MUST read 0.40v to 0.45v. If it does not, the vertical position of the sensor must be changed BY ANY MEANS NESSESARY. a NEW valve will sit higher than an old one......but sometimes not.
There are things you can try to "lengthen" the shaft to increase the voltage reading, such as heat shrink tubing.
This EVP issue is an annoying one (even for experienced mechanics), but has little effect on gas milage, unless it is TRULY stuck open. If it were stuck open.....the truck would be running very rough at idle or die.
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Old 08-18-2009, 07:40 PM   #7
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EGR valve issues?

I do warranties for Ford. And its a known problem. Just like their DPFE sensors.( well not really fords DPFE s it the supplier who makes the junk made in mexico) But the EGR systems on ford are junk have been since late 70's. They fill up full of carbon. SO its always good to have a spare EGR in your truck just keep them cleaned with solvent or a good carbon blaster.
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Old 08-18-2009, 08:10 PM   #8
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EGR valve issues?

i had the same problem on my buick lesabre and got it fixed mpg dubled just a thought
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