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Discussion Starter #1
1998 Taurus SE DOHC Duratec here..

I have to pass inspection next week. it had failed for codes P0171 and P0174. Car seems to have a slight rough idle.

I have done the following:

1. Cleaned EGR.
2. Totally replaced the hard plastic green and red tubing that conects the EGR, EVR and FPR with rubber lines because in removing them to check them for cracks I broke one and decided they seemed to brittle to use.
3. Replaced PCV Valve and it's hose/elbow.

I did clear the codes by having the battery disconnected for an hour while doing those 3 things. But it cam back within a half hour of driving.

I did notice when I remove the boot off the EGR valve that the rough idle goes away instantly. Does this help to pinpoint the problem? Is EVR bad?

Also, if I clear codes again and get to inspection station before codes come back, will it pass inspection or are the codes still in memory?

Thank you. :(
 

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Check the PCV hose, they are prone to cracking and collapsing. If you've ruled out leaks in the vacuum lines, remove the intake manifolds and check the gaskets for leaks. If the engine has higher mileage, and these gaskets have never been replaced, they are highly suspect.

While you have the intake apart, clean the carbon build up from the EGR passage at the throttle body to upper intake. Also remove and clean the gunk build up in the lower intake manifold.


If the inspection station uses a scanner to read the computer, you will not pass. The computer will have a code (P1000) which means the computer has not completed all diagnostics. The inspection station will fail you.
 

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Discussion Starter #3
QUOTE (spridget @ Mar 28 2009, 05:56 PM) index.php?act=findpost&pid=713195
Check the PCV hose, they are prone to cracking and collapsing. If you've ruled out leaks in the vacuum lines, remove the intake manifolds and check the gaskets for leaks. If the engine has higher mileage, and these gaskets have never been replaced, they are highly suspect.

While you have the intake apart, clean the carbon build up from the EGR passage at the throttle body to upper intake. Also remove and clean the gunk build up in the lower intake manifold.


If the inspection station uses a scanner to read the computer, you will not pass. The computer will have a code (P1000) which means the computer has not completed all diagnostics. The inspection station will fail you.[/b]
Forgot to mention that - I did check the PCV hose. I replaced that 90 degree with a piece of tubing as well since it indeed was cracked. Codes remained.
 

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Discussion Starter #4
Why would the rough idle go away when I remove the vacuum line from the EGR? Does this help in figuring out what is to blame for the rough idle? Could it be the EVR or DPFE?
 

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Discussion Starter #6
QUOTE (spridget @ Mar 28 2009, 09:52 PM) index.php?act=findpost&pid=713258
is the vacuum line to the EGR pulling vacuum at idle? It should not. If it is, the EGR is opening when it should not. Removing the line is allowing the EGR to close, like it should be.[/b]
Yes, there is vacuum on the EGR at idle. The EGR vacuum solenoid controls this, doesn't it? I am going to check the voltage on this sensor (EGR vacuum sol. and the DPFE, if I can get to it........

Going to use these instructions to check DPFE votlage: http://free-auto-repair-advice.blogspot.co...egr-system.html

Not sure on checking the EGR sol. voltage though.
 

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You can unplug the solenoid. This will tell you if there is power keeping it on or if it is stuck on.

If it stuck on you may just need to whack it. If it happens again then it needs changed.

It appears from the wire diagram there is 12V on the solenoid all the time the key is on and that the PCM then grounds the circuit to actually turn it on. So there may be a shorted wire that runs from the EGR solenoid to the PCM. This would be a brown and pink wire. You can check this with the key off and see if there is any continuity to ground on that wire.
 

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Discussion Starter #8
QUOTE (SHOZ123 @ Mar 29 2009, 02:30 PM) index.php?act=findpost&pid=713386
You can unplug the solenoid. This will tell you if there is power keeping it on or if it is stuck on.

If it stuck on you may just need to whack it. If it happens again then it needs changed.

It appears from the wire diagram there is 12V on the solenoid all the time the key is on and that the PCM then grounds the circuit to actually turn it on. So there may be a shorted wire that runs from the EGR solenoid to the PCM. This would be a brown and pink wire. You can check this with the key off and see if there is any continuity to ground on that wire.[/b]
Ok, so I set my SunPro 7678 Multimeter to 200ohm (tone mode) and got no tone between the pink/brown wire and ground which tells me Circuit is open? I am just testing the connector to the EGR solenoid with it not connected, correct?

If that was done right, I want to test this hidden DPFE voltage now.
 

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Don't use the tone feature. That is more for diode checking.

Set the meter on ohms and then touch the two leads together and observer the reading. This is the amount you will subtract from the reading you get.

Then check the wire for a reading. Should be less than 1 ohm.
 

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Discussion Starter #10
QUOTE (SHOZ123 @ Mar 29 2009, 07:52 PM) index.php?act=findpost&pid=713449
Don't use the tone feature. That is more for diode checking.

Set the meter on ohms and then touch the two leads together and observer the reading. This is the amount you will subtract from the reading you get.

Then check the wire for a reading. Should be less than 1 ohm.[/b]
Tone mode is 200ohms, lowest range, yes? Other settings are 2k, 20k, 200k and 20m, way above the range we need. And when I put the two leads together the read goes to zero. Perhaps you are confusing multimeters or am I not seeing something.

Here is manual/pdf for my mulimeter: http://www.atlanticz.ca/zclub/techtips/ele...ecks/cp7678.pdf

Also, on page 14 in that PDF there is instruction on how to test a solenoid. Can I test my EGR vacuum solenoid this way?
 

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Discussion Starter #13
QUOTE (SHOZ123 @ Mar 30 2009, 12:35 PM) index.php?act=findpost&pid=713661
Well did you read your manual?[/b]
Yes. What did I miss?

"Testing Solenoids and Relays
This test checks to see if a solenoid or relay
have a broken coil. If the coil tests good, it is
still possible that the relay or solenoid are
defective. The relay can have contacts that
are welded or worn down, and the solenoid
may stick when the coil is energized. This test
does not check for those potential problems."

My EGR vacuum solenoid is open ALL of the time. I will replace this and report back.
 

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Didi you see if the EGR wiring is grounded with the key on?
 

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Discussion Starter #18
Ok, so I finally replaced the EGR vacuum solenoid with new one. No more vacuum on EGR valve at idle, no more stumbling at idle - that problem fixed. Service Engine light still on though. Why? I have driven about 15 miles since putting the new solenoid in and light still on. Should I disconnect + cable for a few hours?
 

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Can't hurt to remove the neg. battery cable for a bit and then reconnect, let the car relearn itself.
 
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