EGR Valve

I have a 97 Buick LaSabre with 93,000 miles. The check engine light came on and the mechanic said the reading was due to insufficient air flow at the egr valve. He reset it, test drove it, and said that the
valve may need to be cleaned if it came on again. (He is a great guy and didn't even charge me for the service.)
After a few hundred miles the light came back on. I purchased a code reader of my own and found 2 readings. Both were insufficient air flow at the egr valve. I deleted the codes and went several hundred miles again before the light came on. I removed the valve and cleaned it as best I could and replaced it with a new gasket. Several hundred miles later, same thing. Always the code is entered twice.
I have noticed that when the light first comes on it is as I start to decelerate. Due to increased vacuum, I assume.
My NAPA dealer lists a replacement gasket that has a screen.
Now my questions:
Does the computer start checking for this condition immediately after being reset?
Should I try replacing the gasket with one with a screen $18.75 vs $2.50 before replacing the valve?
Is there something besides the valve that could be causing the problem?
Should I just bite the bullet and replace the valve?
If I replace the valve, do you recommend using the gasket with a screen?
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This may sound tacky and cheap, but for problems like this, I would probably go to a junk yard and get a used EGR, put it on the car, and see if your problem goes away. If it does, problem solved. If not, you have a spare EGR valve.
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80 Knight wrote:

Picking one up at the Junk yard sounds like a good plan. I will check into that. A new one is $150 plus. Hate to spend that much just to find out that it didn't help.
Thanks Jack
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Jack wrote:

You probably have carbon built up in the EGR passages. Pull the valve off and use a stiff piece of cable to rod out the passages. Then hit your local parts store or dealer and get a can of GM top cylinder cleaner OR a can of Seafoam (marine stores have it in stock if you cannot find it at another store)Also get enough oil and a filter for a change after your done to get the crap out of the oil. Follow the directions on the can with regard to pouring it into the intake system. It WILL SMOKE LIKE CRAZY when you start pouring it in. Don't do it inside and don't have the exhaust pointed toward anything you value. Once it is poured in and the engine dies, let it soak for 20 minutes at least,longer is better. Start it up and take if for a spirited drive. When you get back change the oil. Pull the EGR valve and clean it good and install the clean screen gasket. Test drive it and see if you get a code now.
--
Steve W.


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Steve W. wrote:

Thanks for the thoughts. I did clean the EGR Valve everything seemed to be freed up so I thought I had it cured. It will go several hundred miles before the check engine light comes on. Always shows the code twice when it does come on.
Reading between the lines I think you are saying that the problem could be pieces of carbon coming loose and plugging the passage intermittently. I suppose that is the reason for the screen.
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The problem is carbon buildup in the passages from the exhaust to the egr valve. Dumping crap in the intake manifold will do nothing to clear the problem because the exhaust is drawn in the intake manifold through the valve. The only way to fix it reliably is to pull the intake manifold and clean out all the passages. This is a common problem in today's cars. If you don't fix it the next problem you will see is insufficient catalyst as the catalytic converter is being degraded by excessive fuel. Also dumping all that crap as suggested in the intake will also affect the converter. So do the job right as there is no quick fix for it....

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I've been following this with interest. I picked up a 95 Pontiac with 3.1 with a very similar problem. It has the digital EGR and it also sets the error light when you 'decelerate'. Sometimes it takes 50 miles, if it's on the interstate. Other times it's in 2 miles. The key is deceleration.
I took the valve assembly off and it was full of brown mud. I cleaned everything up but obviously didn't get everything because it still happens. I'll have to do it again I guess until I get it all clean.
By the way, I got the car for a song because it's been doing this for 3 years for the guy and he never had it fixed. The runs great though. Decent mileage. And it just breezed through an emissions inspection.
Mike

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The valve on the Buick is not a digital one, but doubt that is relevant.
When I cleaned the one on my Buick it just had some black sooty stuff in it. Cleaning it didn't seem to help. If I get the problem cured I'll try to let you know what worked. When I first started cleaning the valve would stick open when pushed to the limit. It didn't seem to be sticking after I got done. Could sticking open give the same reading? Seems that would be excessive air flow not insufficient flow but maybe the code would read the same? Mike Y wrote:

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Well, the digital is actually 3 valves in an array. The computer opens from 0 to all 3, making for up to 7 different bypass levels, 8 if you count 'off'. I was told that it's a very common problem on these that the 'small' valve clogs and the indication is as described. I guess the other two are still working fine. Anyway, I cleaned it appeared to help, but not fix it. So I suspect I'm going to have to clean it again and again until it's finally 'totally' clean.
Thing is, it's EXTREMELY easy to get at. In fact, it's easier to take off and put on than it is to change the air filter!
Mike

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Pardon my ignorance. Please clarify. Did you mean clean the exhaust manifold? It seems the problem would be prior too or at the EGR valve before it got to the intake manifold.
Quite frankly, I don't really understand the purpose of the valve.
Woody wrote:

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In my case, it was the intake that was a mess. I suspect the cause is the hot gases hitting the relatively cool intake manifold and condensing.

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The valve allows exhaust gas to enter the intake manifold to decrease upper cylinder temps and improve emissions. The ports that feed the exhaust to the valve get clogged with carbon and need cleaned out. You can clean the valve as much as you want but the problem wont be fixed until the ports are cleaned....

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Just curious, have you noticed a dramatic decrease in fuel economy?

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Not really. It is hard to check the mileage on this car. After the pump first kicks off one can still put in about 2 gallons before it is really full so it is hard to fill it the same each time. I have had as high as 36 mpg which I think was due to not getting the tank as full that time. Usually gets about 29 mpg which I think is good for that large of a car.
I have only owned the car for about 7000 miles so don't really know what it should get.
The light first came on after I had owned it for about 1500 miles.
Why do you ask?
jay420 wrote:

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Changes in fuel consumption rate can be indicative of problems.
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Technical Description Insufficient EGR Flow
What does that mean? EGR stands for Exhaust Gas Recirculation. It is part of the vehicle emmissions system, and is used to reduce combustion temperature and pressure to control Oxides of Nitrogen. There are generally three parts to the EGR system: the EGR valve, an actuator solenoid, and a differential pressure sensor (DPF). These things work together to deliver the correct amount of recirculation based on engine temperature, load, etc. The P0401 code means that OBD detected an insufficient amount of EGR.
Symptoms You may notice drivability problems such as pinging (a.k.a. pre-ignition knock) when the engine is under load or the vehicle is at higher speeds. There may also be other symptoms.
Causes A code P0401 most likely means one or more of the following has happened:
a.. The DPF (differential pressure) sensor is faulty and needs to be replaced b.. There is a blockage in the EGR (most likely carbon buildup) c.. The EGR valve is faulty d.. The EGR valve may not be opening due to a lack of vaccuum Possible Solutions In fixing this code, it is quite common for people to just replace the EGR valve only to have the OBD code return. The EGR valve is not always the culprit.
a.. Use a vacuum pump and pull the EGR valve open while monitoring engine RPM's. There should be a noticable difference in RPM's with the EGR open b.. Clean out the EGR valve to remove deposits c.. Replace the DPF sensor d.. Replace the EGR valve
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