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Old 10-08-2005, 09:00 AM
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EGR valve excessive flow code PO402

1997 Mercury XR7 with the 4.6L w-code engine. Check engine light came on so I got it scanned: code PO402 which is excessive gas flow through the EGR valve. I popped the vacuum line off and it seemed to me that it may not have enough vacuum (I could just be full of it). Anyone here know how much vacuum I should have to power the valve? Any other experience that says this isn't the EGR but something else really simple?

The OEM part at Napa is $72 so I'm trying to be sure it's the valve! Any help is appreciated.

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Old 10-08-2005, 02:25 PM
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it most likely means the EGR is worn out or its getting stuck in the open position.
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Old 10-08-2005, 03:08 PM
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Have you removed the valve itself and checked it for carbon or excessive soot? May be able to clean it out and be done with it. If it is getting excessive gas flow,it sounds as if it is not closing because something is holding the valve in the full or partial open position.EGR valves get extremely hot and are subject to carbon buildup rather quickly.Try cleaning it first and checking for correct operation.
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Old 10-08-2005, 03:13 PM
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yeah... what he said. if its mechanical and not electronic you should be able to use either carb cleaner or brake parts cleaner to help get that crap out of there. but if its electronic you dont want to get that carb cleaner in there it'll ruin it.
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Old 10-08-2005, 03:31 PM
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At my school auto tech class I am doing a head gasket job W/ another student on a '93 Merc Sable w/ sohc 4.6, it had some EGR problems ( flowing too much ) itself, the people who own it ( the kid that is working on it with me's, parents ) clamped down a pair of vise grips onto the hose to block it off. If the grips are not there, the air box howels.
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Old 10-08-2005, 04:26 PM
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Drove it today. Left home and the check engine light was on (assuming the EGR problem). Engine ran a bit poorer, not as much power. On the way home the light was out and it ran great.

Hopefully it is just too much carbon build up and some brake cleaner can do the trick. I'll try to free up enough time to take it off tomorrow. The weather here is nasty today and I don't have anywhere indoors to work on it.
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Old 10-08-2005, 04:56 PM
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yeah tell me about it... i live maybe an hour or 2 from there and its been cold and rainy here... cant even go tot he track its so nasty...
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Old 10-08-2005, 11:18 PM
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I see this code alot on fords at our shop. 9 out of 10 times its the DPFE sensor bad "digital pressure feedback EGR" . Ford has a new design sensor moisture gets in the old style and ruins it. Also ford has a problem esp on the 4.6 with the EGR ports clogging in the throttle body not letting enough flow. Best way to check this is to put a vacuum pump on the EGR with engine idling if the engine stumbles and runs rough its O.K. If not remove the throttle body and clean out the ports, You will not have Vacuum on the egr at all times, The computer controls the EGR solenoid and turns it on under loads and decel etc. Most likely its the DPFE sensor.
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Old 10-09-2005, 10:14 AM
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I can tell you it's definitely NOT the EGR valve. I started the car, popped off the vacuum hose from the valve & plugged it. Then I plugged in a 3ft length. Applied a vacuum to it and the engine bogged. Released the vacuum and the EGR valve made a 'tink' type sound & the engine ran normal again. Repeated several times with the same results. Then I drove the car around the block to warm it up. Came back and did the same test and it returned the same results.

Now about that DPFE sensor, you said:
Ford has a new design sensor moisture gets in the old style and ruins it.

Interestingly enough, it was cool & raining the day this happened. Yesterday afternoon & today it's been dry. Where is the DPFE sensor located so I can see if the connector is corroded or open to the elements?

Thanks fellas, all good help thus far
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Old 10-09-2005, 01:28 PM
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Its an aluminum box bolted to the back of the throttle body about 2 inches square and 1/2 in. thick has 2 rubber hoses hooked to it and 1 three wire connector. Its kinda hard to see it but its there . And its a bit of a bugger to change.
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Old 10-10-2005, 06:05 PM
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Thanks Deuce.

The DPFE sensor was actually bolted to a flange that was bolted to the back of the intake manifold, up under the cowl. Talk about a pain in the arse. Not a lot of room to work behind the intake, under the cowl, and right where the heater core lines run through the firewall. Took it out and found that one of the hoses was split right up at the top. It looks like the intake was already replaced sometime in it's life, and the mechanic had a hard time getting the hoses on it. There isn't much room so I couldn't get the rubber hoses off to replace them. So I just put it back on and used a hose clamp at an attempt at sealing it off. None of the connections had clamps, should they?

Drove it around the block again without any problems. Now I'm just waiting to see if it does it again.
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Old 10-10-2005, 08:10 PM
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No clamps on those hoses all they do is transfere the pressure feedback from the egr pipe to the sensor, so the computer can control the egr accordingly. That DPFE has been updated you should really replace it while you have it off the last one I bought was around 60.00. If you got the hose back on properly with no leaks it may be ok for a while but if code resets you will need to replace sensor and possibly the hoses. Hoses are special heat resistant so just any ole hose wont last long. Good Luck Ed
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Old 11-21-2005, 07:25 PM
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Hey I know it's been over a month now but I just wanted to let everyone know that the DPFE sensor had gone bad. The check engine light came on again about a week later. I replaced the sensor and haven't had any problems since.

Thanks again to 67 Deuce 4 Me for all the good info.
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Old 11-21-2005, 07:59 PM
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Your welcome And thanks for the update.
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