Check engine light

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  #1  
Old 09-22-05, 07:44 PM
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Exclamation Check engine light

I have 1990 Merc Cougar, V6, 3,8L. For the past week every morning check engine light is on, so I took it to the shop to read codes. They told me that EGR vacuum regulator solenoid + EGR valve + DPFE sensor needs to be replaced. Hope, I got it right... Now, the question is , how serious is that? Can and should I drive given that light comes on only in the morning and after car sits for a little bit it's not seen again until next morning. They explained to me that valve is getting clogged and when it closes completely it will cause it to choke. Is that sounds right? Also, if I'm to do it myself is there anything particularly complicated about it? I'm fairly good. What's your take on this? Any advice is appreciated.
 
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  #2  
Old 09-23-05, 07:25 AM
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Depending on what is actually wrong with the egr system, the worst that can happen is that you'll have a poor idle and the engine may want to stall during idle. If that's not your experience, then there will be no damage to your engine.

Their explanation, "valve is getting clogged and when it closes completely it will cause it to choke" is not correct. If the egr valve closes completely, the engine will run great. The problem is when deposits form and the valve cannot close completely, resulting in the abovementioned poor idle.

If you're willing to do some checks yourself, you can apply vacuum to the egr valve to check operation of the valve diaphragm and make sure it moves freely with vacuum. Then you can remove the egr valve and see if you can blow air across the poppet valve. If the poppet valve is leaking, then you've found the problem. If the egr valve checks out okay, then the problem is somewhere else like the solenoid.

Of course, you can always fabricate a plate of steel to block the flow of gases. Problem solved.
 
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Old 09-24-05, 08:41 AM
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They actually said that it will idle poorly. Now, what is the poppet valve? And I can't find anything named DPFE sensor in Chilton's. What it does and where is it? How it's related to EGR valve and solenoid?
 
  #4  
Old 09-24-05, 10:26 AM
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The poppet valve is the business end or guts of the egr valve. A flip through the dictionary would help.

Not everything they said necessarily needs to be replaced. A code came up, and they'll replace everything related to the code to guarantee a fix. If you do it yourself, you can go through each component, one-by-one, starting with the most likely cause and save yourself from replacing potentially good parts.

I don't know what a DPFE sensor is.
 
  #5  
Old 09-25-05, 12:16 PM
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Start by avoiding that shop like the plgue.... if they can't get a simple system like EGR right......

On your car the *most likely* cause is the DPFE sensor... a known area of concern on Fords. These senors aren't very spendy so you may opt for replacement without testing (Ford has a "new" streamlined diagnostic for this sensor.... for a code P0401, replace the sensor... if the code returns, diagnose...). On occasion, we will see a leaking vacuum regulator but it can be rare to see a bad EGR valve.

For the 3.8 motor... I recall that this motor runs "ported" EGR. That is to say that there is a separate passage directing EGR gases to each intake port. If several of these passages are crudded off, one or two cylinders may get too much flow... this rarely sets a code but offers some bad drivability concerns.

HTH
 
  #6  
Old 09-25-05, 06:41 PM
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So what DPFE sensor does? What do you mean by drivability concerns? Do you mean if I keep on driving it? For now it drives fine. Sorry for the dumb questions, but I'd like to get to know as much as possible. Also, like I've said before, I can't find DPFE sensor in Chilton's book.

Thanks for your help. Irina
 
  #7  
Old 09-25-05, 07:53 PM
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Originally Posted by mechanic
Start by avoiding that shop like the plgue.... if they can't get a simple system like EGR right......

I agree with that. It's probably the sensor if the car runs fine. Get the codes read for free at autozone and if its a code P0401 or P0402 the sensor likely is bad as mentioned. In the Chiltons manual, the sensor might be refered to as an egr backpressure sensor, egr pressure sensor, or egr valve position sensor.
 
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Old 09-25-05, 08:16 PM
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It's 1990 Merc, autozone said the car is too old for their computer to read it. How do I apply vacuum to the EGR valve?

Thanks
 
  #9  
Old 09-26-05, 05:48 AM
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The way I do it -- a short length of vacuum hose and your mouth.

Here's how you read the codes, it can be done at home:

early Ford Mo Co code reading
 
  #10  
Old 09-26-05, 07:23 AM
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suspect plugged passage in intake

Remove egr valve completely and you will find almost no change in idle because passage is blocked

With a clear passage, car will idle very poorly or not at all, and you will have considerable vacuum at port on intake. Cover port with your thumb and idle will smooth out. Again, this is what you want to find. If you find little change in idle with thumb on or thumb off, you found your problem, a block passage.

Stay away from the shop. How likely is it that three things will fail at once? A little common sense always helps.

You want your egr system to work. it cuts down on pollution allows your spark to advance as much as possible without knocking and this will give you slightly better gas mileage.

Your code was probably "insufficient egr detected” Since the light doen't stay on you have a progrssive problem. The self-diagnostic detects a problem but driving conditions have not triggered the problem.
 
  #11  
Old 09-27-05, 06:39 AM
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Checked EGR valve with the vacuum, it seems to move OK. Found that the vacuum hose that goes to the valve has melted in a couple of spots. Hope that's all it is causing the light to go on. Will see if it'll come back tomorrow in the morning. Thanks all for your help.
Irina
 
  #12  
Old 09-30-05, 08:13 AM
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The light stayed off for one morning and now back. I removed vacuum hose off the valve and there's no difference in idle that I can see. Also didn't feel much vacuum going on in the hose itself. Should the vacuum be substantial that I can feel it? So which one of the components do I start with?
Thanks. Irina
 
  #13  
Old 09-30-05, 08:28 AM
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The egr is activated only during off-idle.
 
  #14  
Old 09-30-05, 11:02 AM
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I've tried to see if there's any difference on the gear (switched to N,R and D ) and some acceleration with vac hose off and/or vac intake closed on the valve and again there is no diff that I can see. What I'm doing wrong? What happened though is my ABS light came on and brake pedal got hard. After I connected vac hose back to the valve and about 10 min of driving without brakes it all went away and brakes came back. Are ABS related to EGR?
 
  #15  
Old 09-30-05, 12:17 PM
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Not related per se, but disconnecting the vacuum line to the egr messed up the vacuum available to the power braking system. When you disconnect a vacuum line for any reason - such as for diagnostic purposes - it is good form to cap off the vacuum line. I keep a set of golf tees in my tool box for just such purpose.

Have you tried doing the second test I proposed in my first post ("... remove the egr valve and see if you can blow air across the poppet valve...")?, or putting a piece of steel to block the flow of gases?
 
  #16  
Old 10-01-05, 06:34 AM
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DPFE is Digital Pressure Feedback EGR ( I have seen some manuals call it Delta instead of Digital ) On the 3.8l it is on the upper intake near the egr valve. I believe on that model is square,1.5 inches X 1.5 inches has one hose going to a small pipe coming off the Egr valve (not a vacuum hose )and this tells your computer how much back pressure is on the exhaust system, the egr opens pressure goes down ,egr closes pressure goes up.Not to sound like I ve seen a hundred and one of them bad and if the vehicle is in decent shape, not butchered,and you can put it on and not break the sensor or the hose to the egr it will take care of your problem. I havent seen but a very few of those egr valves bad or the vacuum switching valve bad. the vsv were bad about going bad in the 80's but they redisgned it.Also that egr is a pressure egr and has to have back pressure to help open it.There is a bleed off on the pintle on the egr and it needs backpressure to push the pintle up to close off the bleed so vacuum will be able to open it.( usually slightly off idle under a load )So some of the testing can be kinda backwards thinking. Put the DPFE sensor on it. A good ford parts guy will know exectly where on the shelf they are, its that common of a problem.
 
  #17  
Old 10-01-05, 07:00 PM
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Is aftermarket part any good? Or I should order from Ford (they don't stack)
 
  #18  
Old 10-03-05, 06:45 AM
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Engine codes

Read the engine codes: Key on Eng Off: 31 31 1 32 32 and another time it gave 31 31 1 33 33. With engine On it read 31 74 31 74. Does it help to narrow it down to a certain component?
 
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